rc.1 (48656B)
1 .\" rc.1 2 .\"------- 3 .\" Man page portability notes 4 .\" 5 .\" These are some notes on conventions to maintain for greatest 6 .\" portability of this man page to various other versions of 7 .\" nroff. 8 .\" 9 .\" When you want a \ to appear in the output, use \e in the man page. 10 .\" (NOTE this comes up in the rc grammar, where to print out '\n' the 11 .\" man page must contain '\en'.) 12 .\" 13 .\" Evidently not all versions of nroff allow the omission of the 14 .\" terminal " on a macro argument. Thus what could be written 15 .\" 16 .\" .Cr "exec >[2] err.out 17 .\" 18 .\" in true nroffs must be written 19 .\" 20 .\" .Cr "exec >[2] err.out" 21 .\" 22 .\" instead. 23 .\" 24 .\" Use symbolic font names (e.g. R, I, B) instead of the standard 25 .\" font positions 1, 2, 3. Note that for Xf to work the standard 26 .\" font names must be single characters. 27 .\" 28 .\" Not all man macros have the RS and RE requests (I altered the Ds 29 .\" and De macros and the calls to Ds accordingly). 30 .\" 31 .\" Thanks to Michael Haardt (u31b3hs@cip-s01.informatik.rwth-aachen.de) 32 .\" for pointing out these problems. 33 .\" 34 .\" Note that sentences should end at the end of a line. nroff and 35 .\" troff will supply the correct inter-sentence spacing, but only if 36 .\" the sentences end at the end of a line. Explicit spaces, if given, 37 .\" are apparently honored and the normal inter-sentence spacing is 38 .\" suppressed. 39 .\" 40 .\" DaviD W. Sanderson 41 .\"------- 42 .\" Dd distance to space vertically before a "display" 43 .\" These are what n/troff use for inter-paragraph distance 44 .\"------- 45 .if t .nr Dd .4v 46 .if n .nr Dd 1v 47 .\"------- 48 .\" Ds begin a display, indented .5 inches from the surrounding text. 49 .\" 50 .\" Note that uses of Ds and De may NOT be nested. 51 .\"------- 52 .de Ds 53 .\" .RS \\$1 54 .sp \\n(Ddu 55 .in +0.5i 56 .nf 57 .. 58 .\"------- 59 .\" De end a display (no trailing vertical spacing) 60 .\"------- 61 .de De 62 .fi 63 .in 64 .\" .RE 65 .. 66 .\"------- 67 .\" I stole the Xf macro from the -man macros on my machine (originally 68 .\" "}S", I renamed it so that it won't conflict). 69 .\"------- 70 .\" Set Cf to the name of the constant width font. 71 .\" It will be "C" or "(CW", typically. 72 .\" NOTEZ BIEN the lines defining Cf must have no trailing white space: 73 .\"------- 74 .if t .ds Cf C 75 .if n .ds Cf R 76 .\"------- 77 .\" Rc - Alternate Roman and Courier 78 .\"------- 79 .de Rc 80 .Xf R \\*(Cf \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 81 .. 82 .\"------- 83 .\" Ic - Alternate Italic and Courier 84 .\"------- 85 .de Ic 86 .Xf I \\*(Cf \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 87 .. 88 .\"------- 89 .\" Bc - Alternate Bold and Courier 90 .\"------- 91 .de Bc 92 .Xf B \\*(Cf \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 93 .. 94 .\"------- 95 .\" Cr - Alternate Courier and Roman 96 .\"------- 97 .de Cr 98 .Xf \\*(Cf R \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 99 .. 100 .\"------- 101 .\" Ci - Alternate Courier and Italic 102 .\"------- 103 .de Ci 104 .Xf \\*(Cf I \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 105 .. 106 .\"------- 107 .\" Cb - Alternate Courier and Bold 108 .\"------- 109 .de Cb 110 .Xf \\*(Cf B \& "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" 111 .. 112 .\"------- 113 .\" Xf - Alternate fonts 114 .\" 115 .\" \$1 - first font 116 .\" \$2 - second font 117 .\" \$3 - desired word with embedded font changes, built up by recursion 118 .\" \$4 - text for first font 119 .\" \$5 - \$9 - remaining args 120 .\" 121 .\" Every time we are called: 122 .\" 123 .\" If there is something in \$4 124 .\" then Call ourself with the fonts switched, 125 .\" with a new word made of the current word (\$3) and \$4 126 .\" rendered in the first font, 127 .\" and with the remaining args following \$4. 128 .\" else We are done recursing. \$3 holds the desired output 129 .\" word. We emit \$3, change to Roman font, and restore 130 .\" the point size to the default. 131 .\" fi 132 .\" 133 .\" Use Xi to add a little bit of space after italic text. 134 .\"------- 135 .de Xf 136 .ds Xi 137 .\"------- 138 .\" I used to test for the italic font both by its font position 139 .\" and its name. Now just test by its name. 140 .\" 141 .\" .if "\\$1"2" .if !"\\$5"" .ds Xi \^ 142 .\"------- 143 .if "\\$1"I" .if !"\\$5"" .ds Xi \^ 144 .\"------- 145 .\" This is my original code to deal with the recursion. 146 .\" Evidently some nroffs can't deal with it. 147 .\"------- 148 .\" .ie !"\\$4"" \{\ 149 .\" . Xf \\$2 \\$1 "\\$3\\f\\$1\\$4\\*(Xi" "\\$5" "\\$6" "\\$7" "\\$8" "\\$9" 150 .\" .\} 151 .\" .el \{\\$3 152 .\" . ft R \" Restore the default font, since we don't know 153 .\" . \" what the last font change was. 154 .\" . ps 10 \" Restore the default point size, since it might 155 .\" . \" have been changed by an argument to this macro. 156 .\" .\} 157 .\"------- 158 .\" Here is more portable (though less pretty) code to deal with 159 .\" the recursion. 160 .\"------- 161 .if !"\\$4"" .Xf \\$2 \\$1 "\\$3\\f\\$1\\$4\\*(Xi" "\\$5" "\\$6" "\\$7" "\\$8" "\\$9" 162 .if "\\$4"" \\$3\fR\s10 163 .. 164 .TH RC 1 "2015-05-13" 165 .SH NAME 166 rc \- shell 167 .SH SYNOPSIS 168 .B rc 169 .RB [ \-deiIlnopsvx ] 170 .RB [ \-c 171 .IR command ] 172 .RI [ arguments ] 173 .SH DESCRIPTION 174 .I rc 175 is a command interpreter and programming language similar to 176 .IR sh (1). 177 It is based on the AT&T Plan 9 shell of the same name. 178 The shell offers a C-like syntax (much more so than the C shell), 179 and a powerful mechanism for manipulating variables. 180 It is reasonably small and reasonably fast, 181 especially when compared to contemporary shells. 182 Its use is intended to be interactive, 183 but the language lends itself well to scripts. 184 .SH OPTIONS 185 .TP 186 .Cr \-c 187 If 188 .Cr \-c 189 is present, commands are executed from the immediately following 190 argument. 191 Any further arguments to 192 .I rc 193 are placed in 194 .Cr $* . 195 Thus: 196 .Ds 197 .Cr "rc -c 'echo $*' 1 2 3" 198 .De 199 .TP 200 \& 201 prints out 202 .Ds 203 .Cr "1 2 3" 204 .De 205 .TP 206 .Cr \-d 207 This flag causes 208 .I rc 209 not to ignore 210 .Cr SIGQUIT 211 or 212 .Cr SIGTERM . 213 Thus 214 .I rc 215 can be made to dump core if sent 216 .Cr SIGQUIT . 217 This flag is only useful for debugging 218 .IR rc . 219 .TP 220 .Cr \-e 221 If the 222 .Cr \-e 223 flag is present, then 224 .I rc 225 will exit if any command fails (exits with non-zero status). However 226 .I "rc -e" 227 does not exit if a conditional fails. A conditional is the test of an 228 .Cr "if ()" 229 command, the test of a 230 .Cr "while ()" 231 command, or the left hand side of the 232 .Cr || 233 or the 234 .Cr && 235 operator. 236 .TP 237 .Cr \-i 238 If the 239 .Cr \-i 240 flag is present or if the input to 241 .I rc 242 is from a terminal (as determined by 243 .IR isatty (3)) 244 then 245 .I rc 246 will be in 247 .I interactive 248 mode. 249 That is, a prompt (from 250 .Cr $prompt(1)\^ ) 251 will be printed before an input line is taken, and 252 .I rc 253 will ignore 254 .Cr SIGINT . 255 .TP 256 .Cr \-I 257 If the 258 .Cr \-I 259 flag is present, or if the input to 260 .I rc 261 is not from a terminal, then 262 .I rc 263 will not be in interactive mode. 264 No prompts will be printed, and 265 .Cr SIGINT 266 will cause 267 .I rc 268 to exit. 269 .TP 270 .Cr \-l 271 If the 272 .Cr \-l 273 flag is present, or if 274 .IR rc 's 275 .Cr argv[0][0] 276 is a dash 277 .Rc ( \- ), 278 then 279 .I rc 280 will behave as a login shell. 281 That is, it will run commands from 282 .Cr $home/.rcrc , 283 if this file exists, before reading any other input. 284 .TP 285 .Cr \-n 286 This flag causes 287 .I rc 288 to read its input and parse it, but not to execute any commands. 289 This is useful for syntax checking on scripts. 290 If used in combination with the 291 .Cr \-x 292 flag, 293 .I rc 294 will print each command as it is parsed in a form similar to the one 295 used for exporting functions into the environment. 296 .TP 297 .Cr \-o 298 This flag prevents the usual practice of trying to open 299 .Cr /dev/null 300 on file descriptors 0, 1, and 2, if any of those descriptors 301 are inherited closed. 302 .TP 303 .Cr \-p 304 This flag prevents 305 .I rc 306 from initializing shell functions from the environment. 307 This allows 308 .I rc 309 to run in a protected mode, whereby it becomes more difficult for 310 an 311 .I rc 312 script to be subverted by placing false commands in the environment. 313 (Note that the presence of this flag does 314 .I not 315 mean that it is safe to run setuid 316 .I rc 317 scripts; the usual caveats about the setuid bit still apply.) 318 .TP 319 .Cr \-s 320 This flag causes 321 .I rc 322 to read from standard input. 323 Any arguments are placed in 324 .Cr $* . 325 .TP 326 .Cr \-v 327 This flag causes 328 .I rc 329 to echo its input 330 to standard error as it is read. 331 .TP 332 .Cr \-x 333 This flag causes 334 .I rc 335 to print every command on standard error before it is executed. 336 It can be useful for debugging 337 .I rc 338 scripts. 339 .PP 340 .SH COMMANDS 341 A simple command is a sequence of words, separated by white space 342 (space and tab) characters that ends with a newline, semicolon 343 .Rc ( ; ), 344 or ampersand 345 .Rc ( & ). 346 The first word of a command is the name of that command. 347 If the name begins with 348 .Cr / , 349 .Cr ./ , 350 or 351 .Cr ../ , 352 then the name is used as an absolute path 353 name referring to an executable file. 354 Otherwise, the name of the command is looked up in a table 355 of shell functions, builtin commands, 356 or as a file in the directories named by 357 .Cr $path . 358 .SS "Background Tasks" 359 A command ending with 360 .Cr & 361 is run in the background; that is, 362 the shell returns immediately rather than waiting for the command to 363 complete. 364 Background commands have 365 .Cr /dev/null 366 connected to their standard input unless an explicit redirection for 367 standard input is used. 368 .SS "Subshells" 369 A command prefixed with an at-sign 370 .Rc ( @ ) 371 is executed in a subshell. 372 This insulates the parent shell from the effects 373 of state changing operations such as a 374 .B cd 375 or a variable assignment. 376 For example: 377 .Ds 378 .Cr "@ {cd ..; make}" 379 .De 380 .PP 381 will run 382 .IR make (1) 383 in the parent directory 384 .Rc ( .. ), 385 but leaves the shell running in the current directory. 386 .SS "Line continuation" 387 A long logical line may be continued over several physical lines by 388 terminating each line (except the last) with a backslash 389 .Rc ( \e ). 390 The backslash-newline sequence is treated as a space. 391 A backslash is not otherwise special to 392 .IR rc . 393 (In addition, 394 inside quotes a backslash loses its special meaning 395 even when it is followed by a newline.) 396 .SS Quoting 397 .IR rc 398 interprets several characters specially; special characters 399 automatically terminate words. 400 The following characters are special: 401 .Ds 402 .Cr "# ; & | ^ $ \` ' { } ( ) < >" 403 .De 404 .PP 405 The single quote 406 .Rc ( ' ) 407 prevents special treatment of any character other than itself. 408 All characters, including control characters, newlines, 409 and backslashes between two quote characters are treated as an 410 uninterpreted string. 411 A quote character itself may be quoted by placing two quotes in a row. 412 The minimal sequence needed to enter the quote character is 413 .Cr '''' . 414 The empty string is represented by 415 .Cr '' . 416 Thus: 417 .Ds 418 .Cr "echo 'What''s the plan, Stan?'" 419 .De 420 .PP 421 prints out 422 .Ds 423 .Cr "What's the plan, Stan?" 424 .De 425 .PP 426 The number sign 427 .Rc ( # ) 428 begins a comment in 429 .IR rc . 430 All characters up to but not including the next newline are ignored. 431 Note that backslash continuation does not work inside a comment, 432 i.e., 433 the backslash is ignored along with everything else. 434 .SS Grouping 435 Zero or more commands may be grouped within braces 436 .Rc (`` { '' 437 and 438 .Rc `` } ''), 439 and are then treated as one command. 440 Braces do not otherwise define scope; 441 they are used only for command grouping. 442 In particular, be wary of the command: 443 .Ds 444 .Cr "for (i) {" 445 .Cr " command" 446 .Cr "} | command" 447 .De 448 .PP 449 Since pipe binds tighter than 450 .Cr for , 451 this command does not perform what the user expects it to. 452 Instead, enclose the whole 453 .Cr for 454 statement in braces: 455 .Ds 456 .Cr "{for (i) command} | command" 457 .De 458 .PP 459 Fortunately, 460 .IR rc 's 461 grammar is simple enough that a (confident) user can 462 understand it by examining the skeletal 463 .IR yacc (1) 464 grammar 465 at the end of this man page (see the section entitled 466 .BR GRAMMAR ). 467 .SS "Input and output" 468 .PP 469 The standard output may be redirected to a file with 470 .Ds 471 .Cr "command > file" 472 .De 473 .PP 474 and the standard input may be taken from a file with 475 .Ds 476 .Cr "command < file" 477 .De 478 .PP 479 Redirections can appear anywhere in the line: the word 480 following the redirection symbol is the filename and must be 481 quoted if it contains spaces or other special characters. 482 These are all equivalent. 483 .Ds 484 .Cr "echo 1 2 3 > foo" 485 .Cr "> foo echo 1 2 3" 486 .Cr "echo 1 2 > foo 3" 487 .De 488 .PP 489 File descriptors other than 0 and 1 may be specified also. 490 For example, to redirect standard error to a file, use: 491 .Ds 492 .Cr "command >[2] file" 493 .De 494 .PP 495 In order to duplicate a file descriptor, use 496 .Ci >[ n = m ]\fR. 497 Thus to redirect both standard output and standard error 498 to the same file, use 499 .Ds 500 .Cr "command > file >[2=1]" 501 .De 502 .PP 503 As in 504 .IR sh , 505 redirections are processed from left to right. 506 Thus this sequence 507 .Ds 508 .Cr "command >[2=1] > file" 509 .De 510 .PP 511 is usually a mistake. 512 It first duplicates standard error to standard 513 output; then redirects standard output to a file, leaving standard error 514 wherever standard output originally was. 515 .PP 516 To close a file descriptor that may be open, use 517 .Ci >[ n =]\fR. 518 For example, to 519 close file descriptor 7: 520 .Ds 521 .Cr "command >[7=]" 522 .De 523 .PP 524 Note that no spaces may appear in these constructs: 525 .Ds 526 .Cr "command > [2] file" 527 .De 528 .PP 529 would send the output of the command to a file named 530 .Cr [2] , 531 with the intended filename appearing in the command's argument list. 532 .PP 533 In order to place the output of a command at the end of an already 534 existing file, use: 535 .Ds 536 .Cr "command >> file" 537 .De 538 .PP 539 If the file does not exist, then it is created. 540 .PP 541 ``Here documents'' are supported as in 542 .I sh 543 with the use of 544 .Ds 545 .Cr "command << 'eof-marker'" 546 .De 547 .PP 548 Subsequent lines form the standard input of 549 the command, till a line containing just the 550 marker, in this case 551 .Cr eof-marker , 552 is encountered. 553 .PP 554 If the end-of-file marker is enclosed in quotes, 555 then no variable substitution occurs inside the here document. 556 Otherwise, every variable is substituted 557 by its space-separated-list value (see 558 .BR "Flat Lists" , 559 below), 560 and if a 561 .Cr ^ 562 character follows a variable name, it is deleted. 563 This allows the unambiguous use of variables adjacent to text, as in 564 .Ds 565 .Cr $variable^follow 566 .De 567 .PP 568 To include a literal 569 .Cr $ 570 in a here document when an unquoted end-of-file marker is being used, 571 enter it as 572 .Cr $$ . 573 .PP 574 Additionally, 575 .I rc 576 supports ``here strings'', which are like here documents, 577 except that input is taken directly from a string on the command line. 578 Their use is illustrated here: 579 .Ds 580 .Cr "cat <<< 'this is a here string' | wc" 581 .De 582 .PP 583 (This feature enables 584 .I rc 585 to export functions using here documents into the environment; 586 the author does not expect users to find this feature useful.) 587 .SS Pipes 588 Two or more commands may be combined in a pipeline by placing the 589 vertical bar 590 .Rc ( \||\| ) 591 between them. 592 The standard output (file descriptor 1) 593 of the command on the left is tied to the standard input (file 594 descriptor 0) of the command on the right. 595 The notation 596 .Ci |[ n = m ] 597 indicates that file descriptor 598 .I n 599 of the left process is connected to 600 file descriptor 601 .I m 602 of the right process. 603 .Ci |[ n ] 604 is a shorthand for 605 .Ci |[ n =0]\fR. 606 As an example, to pipe the standard error of a command to 607 .IR wc (1), 608 use: 609 .Ds 610 .Cr "command |[2] wc" 611 .De 612 .PP 613 As with file redirections, no spaces may occur in the construct specifying 614 numbered file descriptors. 615 .PP 616 The exit status of a pipeline is considered true if and only if every 617 command in the pipeline exits true. 618 .SS "Commands as Arguments" 619 Some commands, like 620 .IR cmp (1) 621 or 622 .IR diff (1), 623 take their arguments on the command 624 line, and do not read input from standard input. 625 It is convenient 626 sometimes to build nonlinear pipelines so that a command like 627 .I cmp 628 can read the output of two other commands at once. 629 .I rc 630 does it like this: 631 .Ds 632 .Cr "cmp <{command} <{command}" 633 .De 634 .PP 635 compares the output of the two commands in braces. 636 Note: since this form of 637 redirection is implemented with some kind of pipe, and since one cannot 638 .IR lseek (2) 639 on a pipe, commands that use 640 .IR lseek (2) 641 will hang. 642 For example, some versions of 643 .IR diff (1) 644 use 645 .IR lseek (2) 646 on their inputs. 647 .PP 648 Data can be sent down a pipe to several commands using 649 .IR tee (1) 650 and the output version of this notation: 651 .Ds 652 .Cr "echo hi there | tee >{sed 's/^/p1 /'} >{sed 's/^/p2 /'}" 653 .De 654 .SH "CONTROL STRUCTURES" 655 The following may be used for control flow in 656 .IR rc : 657 .SS "If-Else Statements" 658 .PD 0 659 .sp 660 .Ci "if (" test ") {" 661 .br 662 .I " cmd" 663 .br 664 .TP 665 .Ci "} else " cmd 666 The 667 .I test 668 is executed, and if its return status is zero, the first 669 command is executed, otherwise the second is. 670 Braces are not mandatory around the commands. 671 However, an 672 .Cr else 673 statement is valid only if it 674 follows a close-brace on the same line. 675 Otherwise, the 676 .Cr if 677 is taken to be a simple-if: 678 .Ds 679 .Cr "if (test)" 680 .Cr " command" 681 .De 682 .PD 683 .SS "While and For Loops" 684 .TP 685 .Ci "while (" test ) " cmd" 686 .I rc 687 executes the 688 .I test 689 and performs the command as long as the 690 .I test 691 is true. 692 .TP 693 .Ci "for (" var " in " list ) " cmd" 694 .I rc 695 sets 696 .I var 697 to each element of 698 .I list 699 (which may contain variables and backquote substitutions) and runs 700 .IR cmd . 701 If 702 .Rc `` in 703 .IR list '' 704 is omitted, then 705 .I rc 706 will set 707 .I var 708 to each element of 709 .Cr $* . 710 For example: 711 .Ds 712 .Cr "for (i in \`{ls -F | grep '\e*$' | sed 's/\e*$//'}) { commands }" 713 .De 714 .TP 715 \& 716 will set 717 .Cr $i 718 to the name of each file in the current directory that is 719 executable. 720 .SS "Switch" 721 .TP 722 .Ci "switch (" list ") { case" " ..." " }" 723 .I rc 724 looks inside the braces after a 725 .Cr switch 726 for statements beginning with the word 727 .Cr case . 728 If any of the patterns following 729 .Cr case 730 match the list supplied to 731 .Cr switch , 732 then the commands up until the next 733 .Cr case 734 statement are executed. 735 The metacharacters 736 .Cr "*" , 737 .Cr [ 738 or 739 .Cr ? 740 should not be quoted; 741 matching is performed only against the strings in 742 .IR list , 743 not against file names. 744 (Matching for case statements is the same as for the 745 .Cr ~ 746 command.) 747 .SS "Logical Operators" 748 There are a number of operators in 749 .I rc 750 which depend on the exit status of a command. 751 .Ds 752 .Cr "command && command" 753 .De 754 .PP 755 executes the first command and then executes the second command if and only if 756 the first command exits with a zero exit status (``true'' in Unix). 757 .Ds 758 .Cr "command || command" 759 .De 760 .PP 761 executes the first command and then executes the second command if and only if 762 the first command exits with a nonzero exit status (``false'' in Unix). 763 .Ds 764 .Cr "! command" 765 .De 766 .PP 767 negates the exit status of a command. 768 .SH "PATTERN MATCHING" 769 There are two forms of pattern matching in 770 .IR rc . 771 One is traditional shell globbing. 772 This occurs in matching for file names in argument lists: 773 .Ds 774 .Cr "command argument argument ..." 775 .De 776 .PP 777 When the characters 778 .Cr "*" , 779 .Cr [ 780 or 781 .Cr ? 782 occur in an argument or command, 783 .I rc 784 looks at the 785 argument as a pattern for matching against files. 786 (Contrary to the behavior other shells exhibit, 787 .I rc 788 will only perform pattern matching if a metacharacter occurs unquoted and 789 literally in the input. 790 Thus, 791 .Ds 792 .Cr "foo='*'" 793 .Cr "echo $foo" 794 .De 795 .PP 796 will always echo just a star. 797 In order for non-literal metacharacters to be expanded, an 798 .Cr eval 799 statement must be used in order to rescan the input.) 800 Pattern matching occurs according to the following rules: a 801 .Cr * 802 matches any number (including zero) of 803 characters. 804 A 805 .Cr ? 806 matches any single character, and a 807 .Cr [ 808 followed by a 809 number of characters followed by a 810 .Cr ] 811 matches a single character in that 812 class. 813 The rules for character class matching are the same as those for 814 .IR ed (1), 815 with the exception that character class negation is achieved 816 with the tilde 817 .Rc ( ~ ), 818 not the caret 819 .Rc ( ^ ), 820 since the caret already means 821 something else in 822 .IR rc . 823 .PP 824 .I rc 825 also matches patterns against strings with the 826 .Cr ~ 827 command: 828 .Ds 829 .Cr "~ subject pattern pattern ..." 830 .De 831 .PP 832 The 833 .Cr ~ 834 command succeeds (sets 835 .Cr $status 836 to zero) if and only if one of the 837 .Cr pattern s 838 matches 839 .Cr subject . 840 Thus 841 .Ds 842 .Cr "~ foo f*" 843 .De 844 .PP 845 succeeds (sets status to zero), while 846 .Ds 847 .Cr "~ bar f*" 848 .De 849 .PP 850 fails (sets status to one). 851 .PP 852 The null list is matched by the null list, so 853 .Ds 854 .Cr "~ $foo ()" 855 .De 856 .PP 857 checks to see whether 858 .Cr $foo 859 is empty or not. Because 860 .I rc 861 does not have hierarchical lists, the test for emptiness cannot be 862 combined with other tests. To test whether 863 .Cr $foo 864 is empty, or one of the strings 865 .Cr nada 866 or 867 .Cr rien , 868 do 869 .I not 870 write 871 .Ds 872 .Cr "~ $x () nada rien # WRONG means the same as: ~ $x nada rien" 873 .De 874 .PP 875 instead write 876 .Ds 877 .Cr "~ $x () || ~ $x nada rien" 878 .De 879 .PP 880 Another way to test if 881 .Cr $foo 882 is empty is 883 .Ds 884 .Cr "~ $#foo 0" 885 .De 886 .PP 887 Note that inside a 888 .Cr ~ 889 command 890 .I rc 891 does not match patterns against file 892 names, so it is not necessary to quote the characters 893 .Cr "*" , 894 .Cr [ 895 and 896 .Cr "?" . 897 However, 898 .I rc 899 does expand the subject against filenames if it contains 900 metacharacters. 901 Thus, the command 902 .Ds 903 .Cr "~ * ?" 904 .De 905 .PP 906 succeeds if any of the files in the current directory have a 907 single-character name. 908 .PP 909 If the 910 .Cr ~ 911 command is given a list as its first 912 argument, then a successful match against any of the elements of that 913 list will cause 914 .Cr ~ 915 to succeed. 916 For example: 917 .Ds 918 .Cr "~ (foo goo zoo) z*" 919 .De 920 .PP 921 is true. 922 .SH "LISTS AND VARIABLES" 923 The primary data structure in 924 .IR rc 925 is the list, which is a sequence of words. 926 Parentheses are used to group lists. 927 The empty list is represented by 928 .Cr "()" . 929 Lists have no hierarchical structure; 930 a list inside another list is expanded so the 931 outer list contains all the elements of the inner list. 932 Thus, the following are all equivalent 933 .Ds 934 .Cr "one two three" 935 936 .Cr "(one two three)" 937 938 .Cr "((one) () ((two three)))" 939 .De 940 .PP 941 Note that the null string, 942 .Cr "''" , 943 and the null list, 944 .Cr "()" , 945 are two very different things. 946 Assigning the null string to a variable is a valid operation, but it 947 does not remove its definition. 948 .Ds 949 .Cr "null = '' empty = () echo $#null $#empty" 950 .De 951 .PP 952 produces the output 953 .Ds 954 .Cr "1 0" 955 .De 956 .SS "List Concatenation" 957 Two lists may be joined by the concatenation operator 958 .Rc ( ^ ). 959 Concatenation works according to the following rules: 960 if the two lists have the same number of elements, 961 then concatenation is pairwise: 962 .Ds 963 .Cr "echo (a\- b\- c\-)^(1 2 3)" 964 .De 965 .PP 966 produces the output 967 .Ds 968 .Cr "a\-1 b\-2 c\-3" 969 .De 970 .PP 971 Otherwise, at least one of the lists must have a single element, 972 and then the concatenation is distributive: 973 .Ds 974 .Cr "cc \-^(O g c) (malloc alloca)^.c" 975 .De 976 .PP 977 has the effect of performing the command 978 .Ds 979 .Cr "cc \-O \-g \-c malloc.c alloca.c" 980 .De 981 .PP 982 A single word is a list of length one, so 983 .Ds 984 .Cr "echo foo^bar" 985 .De 986 .PP 987 produces the output 988 .Ds 989 .Cr foobar 990 .De 991 .SS "Free Carets" 992 .I rc 993 inserts carets (concatenation operators) for free in certain situations, 994 in order to save some typing on the user's behalf. 995 For 996 example, the above example could also be typed in as: 997 .Ds 998 .Cr "opts=(O g c) files=(malloc alloca) cc \-$opts $files.c" 999 .De 1000 .PP 1001 .I rc 1002 takes care to insert a free caret between the 1003 .Rc `` \- '' 1004 and 1005 .Cr "$opts" , 1006 as well 1007 as between 1008 .Cr $files 1009 and 1010 .Cr ".c" . 1011 The rule for free carets is as follows: if 1012 a word or keyword is immediately 1013 followed by another word, keyword, dollar-sign or 1014 backquote, then 1015 .I rc 1016 inserts a caret between them. 1017 .SS "Variables" 1018 A list may be assigned to a variable, using the notation: 1019 .Ds 1020 .Ic var " = " list 1021 .De 1022 .PP 1023 The special variable 1024 .Cr * 1025 may also be assigned to using this notation; 1026 .I rc 1027 has no 1028 .B set 1029 builtin. 1030 .PP 1031 Any non-empty sequence of characters, except a sequence including only 1032 digits, may be used as a variable name. 1033 Any character except 1034 .Cr = 1035 may be used, but special characters must be quoted. 1036 All user-defined variables are exported into the environment. 1037 .PP 1038 The value of a variable is referenced with the dollar 1039 .Rc ( $ ) 1040 operator: 1041 .Ds 1042 .Ci $ var 1043 .De 1044 .PP 1045 Any variable which has not been assigned a value returns the null list, 1046 .Cr "()" , 1047 when referenced. 1048 Multiple references are allowed: 1049 .Ds 1050 .Cr "a = foo" 1051 .Cr "b = a" 1052 .Cr "echo $ $ b" 1053 .De 1054 .PP 1055 prints 1056 .Ds 1057 .Cr foo 1058 .De 1059 .PP 1060 A variable's definition may also be removed by 1061 assigning the null list to a variable: 1062 .Ds 1063 .Ic var =() 1064 .De 1065 .PP 1066 For ``free careting'' to work correctly, 1067 .I rc 1068 must make certain assumptions 1069 about what characters may appear in a variable name. 1070 .I rc 1071 assumes that a variable name consists only of alphanumeric characters, 1072 underscore 1073 .Rc ( \|_\| ) 1074 and star 1075 .Rc ( * ). 1076 To reference a variable with other 1077 characters in its name, quote the variable name. 1078 Thus: 1079 .Ds 1080 .Cr "echo $'we$Ird:Variab!le'" 1081 .De 1082 .SS "Local Variables" 1083 Any number of variable assignments may be made local to a single 1084 command by typing: 1085 .Ds 1086 .Cr "a=foo b=bar ... command" 1087 .De 1088 .PP 1089 The command may be a compound command, so for example: 1090 .Ds 1091 .Cr "path=. ifs=() {" 1092 .Cr " " ... 1093 .Cr } 1094 .De 1095 .PP 1096 sets 1097 .Cr path 1098 to 1099 .Cr . 1100 and removes 1101 .Cr ifs 1102 for the duration of one long compound command. 1103 .SS "Variable Subscripts" 1104 Variables may be subscripted with the notation 1105 .Ds 1106 .Ci $var( n ) 1107 .De 1108 .PP 1109 where 1110 .I n 1111 is a list of integers (origin 1). 1112 The opening parenthesis must immediately follow the variable name. 1113 The list of subscripts need not be in order or even unique. 1114 Thus, 1115 .Ds 1116 .Cr "a=(one two three)" 1117 .Cr "echo $a(3 3 3)" 1118 .De 1119 .PP 1120 prints 1121 .Ds 1122 .Cr "three three three" 1123 .De 1124 .PP 1125 If 1126 .I n 1127 references a nonexistent element, then 1128 .Ci $var( n ) 1129 returns the null list. 1130 The notation 1131 .Ci "$" n\fR, 1132 where 1133 .I n 1134 is an integer, is a shorthand for 1135 .Ci $*( n )\fR. 1136 Thus, 1137 .IR rc 's 1138 arguments may be referred to as 1139 .Cr "$1" , 1140 .Cr "$2" , 1141 and so on. 1142 .PP 1143 Note also that the list of subscripts may be given by any of 1144 .IR rc 's 1145 list operations: 1146 .Ds 1147 .Cr "$var(\`{awk 'BEGIN{for(i=1;i<=10;i++)print i;exit; }'})" 1148 .De 1149 .PP 1150 returns the first 10 elements of 1151 .Cr $var . 1152 .PP 1153 To count the number of elements in a variable, use 1154 .Ds 1155 .Cr $#var 1156 .De 1157 .PP 1158 This returns a single-element list, with the number of elements in 1159 .Cr $var . 1160 .SS "Flat Lists" 1161 In order to create a single-element list from a multi-element list, 1162 with the components space-separated, use the dollar-caret 1163 .Rc ( $^ ) 1164 operator: 1165 .Ds 1166 .Cr $^var 1167 .De 1168 .PP 1169 This is useful when the normal list concatenation rules need to be 1170 bypassed. 1171 For example, to append a single period at the end of 1172 .Cr $path , 1173 use: 1174 .Ds 1175 .Cr "echo $^path." 1176 .De 1177 .PP 1178 For compatibility with the Plan 9 rc, 1179 .Ds 1180 .Cr $"var 1181 .De 1182 .PP 1183 is accepted as a synonym for dollar-caret. 1184 .SS "Backquote Substitution" 1185 A list may be formed from the output of a command by using backquote 1186 substitution: 1187 .Ds 1188 .Cr "\`{ command }" 1189 .De 1190 .PP 1191 returns a list formed from the standard output of the command in braces. 1192 .Cr $ifs 1193 is used to split the output into list elements. 1194 By default, 1195 .Cr $ifs 1196 has the value space-tab-newline. 1197 .PP 1198 The braces may be omitted if the command is a single word. 1199 Thus 1200 .Cr \`ls 1201 may be used instead of 1202 .Cr "\`{ls}" . 1203 This last feature can be used to create shortcuts by defining functions that 1204 expand to useful argument lists. 1205 For example: 1206 .Ds 1207 .Cr "fn src { echo *.[chy] }" 1208 .De 1209 .PP 1210 followed by 1211 .Ds 1212 .Cr "wc \`src" 1213 .De 1214 .PP 1215 This will print out a word-count of all C source files in the current 1216 directory. 1217 .PP 1218 In order to override the value of 1219 .Cr $ifs 1220 for a single backquote 1221 substitution, use: 1222 .Ds 1223 .Cr "\`(ifs-list){ command }" 1224 .De 1225 .PP 1226 .Cr $ifs 1227 will be temporarily ignored and the command's output will be split as specified by 1228 the list following the double backquote. 1229 For example: 1230 .Ds 1231 .Cr "\`($nl :){cat /etc/passwd}" 1232 .De 1233 .PP 1234 splits up 1235 .Cr /etc/passwd 1236 into fields. 1237 .PP 1238 As a convenience, 1239 .I rc 1240 defines 1241 .Cr $nl 1242 to contain the newline character, and 1243 .Cr $tab 1244 to contain the tab character. Thus, if you want to process everything in the 1245 current directory, but in a random order, you could use: 1246 .Ds 1247 .Cr "for (f in \`$nl{ls | shuf}) { ... process $f }" 1248 .De 1249 .PP 1250 This will correctly handle filenames that contain spaces. 1251 .PP 1252 Note that 1253 .I rc 1254 scripts that use backquote substitution should avoid relying on the default 1255 values of 1256 .Cr $ifs , 1257 .Cr $nl , 1258 or 1259 .Cr $tab . 1260 Instead, they should explicitly set what they need. 1261 .SH "SPECIAL VARIABLES" 1262 Several variables are known to 1263 .I rc 1264 and are treated specially. 1265 In the following list, ``default'' indicates that 1266 .I rc 1267 gives the variable a default value on startup; ``no-export'' indicates 1268 that the variable is never exported; and ``read-only'' indicates that 1269 an attempt to set the variable will silently have no effect. 1270 .PP 1271 Also, ``alias'' means that the variable is aliased to the same name in 1272 capitals. 1273 For example, an assignment to 1274 .Cr $cdpath 1275 causes an automatic assignment to 1276 .Cr $CDPATH , 1277 and vice-versa. 1278 If 1279 .Cr $CDPATH 1280 is set when 1281 .I rc 1282 is started, its value is imported into 1283 .Cr $cdpath . 1284 .Cr $cdpath 1285 and 1286 .Cr $path 1287 are 1288 .I rc 1289 lists; 1290 .Cr $CDPATH 1291 and 1292 .Cr $PATH 1293 are colon-separated lists. 1294 Only the names spelt in capitals are exported into the environment. 1295 .TP 1296 .Cr * " (no-export)" 1297 The argument list of 1298 .IR rc . 1299 .Cr "$1, $2," 1300 etc. are the same as 1301 .Cr $*(1) , 1302 .Cr $*(2) , 1303 etc. 1304 .TP 1305 .Cr 0 " (default no-export)" 1306 The variable 1307 .Cr $0 1308 holds the value of 1309 .Cr argv[0] 1310 with which 1311 .I rc 1312 was invoked. 1313 Additionally, 1314 .Cr $0 1315 is set to the name of a function for the duration of 1316 the execution of that function, and 1317 .Cr $0 1318 is also set to the name of the 1319 file being interpreted for the duration of a 1320 .Cr . 1321 command. 1322 .Cr $0 1323 is not an element of 1324 .Cr $* , 1325 and is never treated as one. 1326 .TP 1327 .Cr apid " (no-export)" 1328 The process ID of the last process started in the background. 1329 .TP 1330 .Cr apids " (no-export read-only)" 1331 A list whose elements are the process IDs of all background processes 1332 which are still alive, or which have died and have not been waited for 1333 yet. 1334 .TP 1335 .Cr bqstatus " (no-export)" 1336 The exit status of the 1337 .I rc 1338 forked to execute the most recent backquote substitution. Note that, unlike 1339 .Cr $status , 1340 .Cr $bqstatus 1341 is always a single element list (see 1342 .BR "EXIT STATUS" 1343 below). For example: 1344 .Ds 1345 .Cr "echo foo |grep bar; whatis status" 1346 .De 1347 .TP 1348 \& 1349 prints 1350 .Ds 1351 .Cr "status=(0 1)" 1352 .De 1353 .TP 1354 \& 1355 whereas 1356 .Ds 1357 .Cr "x=`{echo foo |grep bar}; whatis bqstatus" 1358 .De 1359 .TP 1360 \& 1361 prints 1362 .Ds 1363 .Cr "bqstatus=1" 1364 .De 1365 .TP 1366 .Cr cdpath " (alias)" 1367 A list of directories to search for the target of a 1368 .B cd 1369 command. 1370 The empty string stands for the current directory. 1371 Note that if the 1372 .Cr $cdpath 1373 variable does not contain the current directory, then the current 1374 directory will not be searched; this allows directory searching to 1375 begin in a directory other than the current directory. 1376 .TP 1377 .Cr history 1378 .Cr $history 1379 contains the name of a file to which commands are appended as 1380 .I rc 1381 reads them. 1382 This facilitates the use of a stand-alone history program 1383 (such as 1384 .IR history (1)) 1385 which parses the contents of the history file and presents them to 1386 .I rc 1387 for reinterpretation. 1388 If 1389 .Cr $history 1390 is not set, then 1391 .I rc 1392 does not append commands to any file. 1393 .TP 1394 .Cr home " (alias)" 1395 The default directory for the builtin 1396 .B cd 1397 command, and the directory in which 1398 .I rc 1399 looks to find its initialization file, 1400 .Cr .rcrc , 1401 if 1402 .I rc 1403 has been started up as a login shell. 1404 .TP 1405 .Cr ifs " (default)" 1406 The internal field separator, used for splitting up the output of 1407 backquote commands for digestion as a list. On startup, 1408 .I rc 1409 assigns the list containing the characters space, tab, and newline to 1410 .Cr $ifs . 1411 .TP 1412 .Cr nl " (default)" 1413 Contains the newline character (see 1414 .BR "Backquote substitution" 1415 above). 1416 .TP 1417 .Cr path " (alias)" 1418 This is a list of directories to search in for commands. 1419 The empty string stands for the current directory. 1420 If neither 1421 .Cr $PATH 1422 nor 1423 .Cr $path 1424 is set at startup time, 1425 .Cr $path 1426 assumes a default value suitable for your system. 1427 This is typically 1428 .Cr "(/usr/local/bin /usr/bin /usr/ucb /bin .)" 1429 .TP 1430 .Cr pid " (default no-export)" 1431 On startup, 1432 .Cr $pid 1433 is initialized to the numeric process ID of the currently running 1434 .IR rc . 1435 .TP 1436 .Cr prompt " (default)" 1437 This variable holds the two prompts (in list form, of course) that 1438 .I rc 1439 prints. 1440 .Cr $prompt(1) 1441 is printed before each command is read, and 1442 .Cr $prompt(2) 1443 is printed when input is expected to continue on the next 1444 line. 1445 .I rc 1446 sets 1447 .Cr $prompt 1448 to 1449 .Cr "('; ' '')" 1450 by default. 1451 The reason for this is that it enables an 1452 .I rc 1453 user to grab commands from previous lines using a 1454 mouse, and to present them to 1455 .I rc 1456 for re-interpretation; the semicolon 1457 prompt is simply ignored by 1458 .IR rc . 1459 The null 1460 .Cr $prompt(2) 1461 also has its 1462 justification: an 1463 .I rc 1464 script, when typed interactively, will not leave 1465 .Cr $prompt(2) 's 1466 on the screen, 1467 and can therefore be grabbed by a mouse and placed 1468 directly into a file for use as a shell script, without further editing 1469 being necessary. 1470 .TP 1471 .Cr prompt " (function)" 1472 If this function is defined, then it gets executed every time 1473 .I rc 1474 is about to print 1475 .Cr "$prompt(1)" . 1476 .TP 1477 .Cr status " (no-export read-only)" 1478 The exit status of the last command. 1479 If the command exited with a numeric value, that number is the status. 1480 If the command died with a signal, the status is the name of that signal; 1481 if a core file was created, the string 1482 .Rc `` +core '' 1483 is appended. 1484 The value of 1485 .Cr $status 1486 for a pipeline is a list, with one entry, as above, for each process 1487 in the pipeline. 1488 For example, the command 1489 .Ds 1490 .Cr "ls | wc" 1491 .De 1492 .TP 1493 \& 1494 usually sets 1495 .Cr $status 1496 to 1497 .Cr "(0 0)" . 1498 .TP 1499 .Cr tab " (default)" 1500 Contains the tab character (see 1501 .BR "Backquote substitution" 1502 above). 1503 .TP 1504 .Cr version " (default)" 1505 On startup, the first element of this list variable is initialized to 1506 a string which identifies this version of 1507 .IR rc . 1508 The second element is initialized to a string which can be found by 1509 .IR ident (1) 1510 and the 1511 .I what 1512 command of 1513 .IR sccs (1). 1514 .SH FUNCTIONS 1515 .I rc 1516 functions are identical to 1517 .I rc 1518 scripts, except that they are stored 1519 in memory and are automatically exported into the environment. 1520 A shell function is declared as: 1521 .Ds 1522 .Cr "fn name { commands }" 1523 .De 1524 .PP 1525 .I rc 1526 scans the definition until the close-brace, so the function can 1527 span more than one line. 1528 The function definition may be removed by typing 1529 .Ds 1530 .Cr "fn name" 1531 .De 1532 .PP 1533 (One or more names may be specified. 1534 With an accompanying definition, all names receive the same definition. 1535 This is sometimes useful 1536 for assigning the same signal handler to many signals. 1537 Without a definition, all named functions are deleted.) 1538 When a function is executed, 1539 .Cr $* 1540 is set to the arguments to that 1541 function for the duration of the command. 1542 Thus a reasonable definition for 1543 .Cr "l" , 1544 a shorthand for 1545 .IR ls (1), 1546 could be: 1547 .Ds 1548 .Cr "fn l { ls -FC $* }" 1549 .De 1550 .PP 1551 but not 1552 .Ds 1553 .Cr "fn l { ls -FC } # WRONG" 1554 .De 1555 .SH "INTERRUPTS AND SIGNALS" 1556 .I rc 1557 recognizes a number of signals, and allows the user to define shell 1558 functions which act as signal handlers. 1559 .I rc 1560 by default traps 1561 .Cr SIGINT 1562 when it is in interactive mode. 1563 .Cr SIGQUIT 1564 and 1565 .Cr SIGTERM 1566 are ignored, unless 1567 .I rc 1568 has been invoked with the 1569 .Cr \-d 1570 flag. 1571 However, user-defined signal handlers may be written for these and 1572 all other signals. 1573 The way to define a signal handler is to 1574 write a function by the name of the signal in lower case. 1575 Thus: 1576 .Ds 1577 .Cr "fn sighup { echo hangup; rm /tmp/rc$pid.*; exit }" 1578 .De 1579 .PP 1580 In addition to Unix signals, 1581 .I rc 1582 recognizes the artificial signal 1583 .Cr SIGEXIT 1584 which occurs as 1585 .I rc 1586 is about to exit. 1587 .PP 1588 In order to remove a signal handler's definition, 1589 remove it as though it were a regular function. 1590 For example: 1591 .Ds 1592 .Cr "fn sigint" 1593 .De 1594 .PP 1595 returns the handler of 1596 .Cr SIGINT 1597 to the default value. 1598 In order to ignore a signal, set the signal handler's value to 1599 .Cr "{}" . 1600 Thus: 1601 .Ds 1602 .Cr "fn sigint {}" 1603 .De 1604 .PP 1605 causes 1606 .Cr SIGINT 1607 to be ignored by the shell. 1608 Only signals that are being ignored are passed on to programs run by 1609 .IR rc ; 1610 signal functions are not exported. 1611 .PP 1612 On System V-based Unix systems, 1613 .I rc 1614 will not allow you to trap 1615 .Cr SIGCLD . 1616 .SH "BUILTIN COMMANDS" 1617 Builtin commands execute in the context of the shell, but otherwise 1618 behave exactly like other commands. 1619 Although 1620 .BR ! , 1621 .B ~ 1622 and 1623 .B @ 1624 are not strictly speaking builtin commands, 1625 they can usually be used as such. 1626 .TP 1627 \&\fB.\fR [\fB\-i\fR] \fIfile \fR[\fIarg ...\fR] 1628 Reads 1629 .I file 1630 as input to 1631 .IR rc 1632 and executes its contents. 1633 With a 1634 .Cr \-i 1635 flag, input is interactive. 1636 Thus from within a shell script, 1637 .Ds 1638 .Cr ". \-i /dev/tty" 1639 .De 1640 .TP 1641 \& 1642 does the ``right thing''. 1643 .TP 1644 .B break 1645 Breaks from the innermost 1646 .Cr for 1647 or 1648 .Cr while , 1649 as in C. 1650 It is an error to invoke 1651 .B break 1652 outside of a loop. 1653 (Note that there is no 1654 .B break 1655 keyword between commands in 1656 .Cr switch 1657 statements, unlike C.) 1658 .TP 1659 \fBbuiltin \fIcommand \fR[\fIarg ...\fR] 1660 Executes the command ignoring any function definition of the 1661 same name. 1662 This command is present to allow functions with the 1663 same names as builtins to use the underlying builtin or binary. 1664 For example: 1665 .Ds 1666 .Cr "fn ls { builtin ls -FC $* }" 1667 .De 1668 .TP 1669 \& 1670 is a reasonable way to pass a default set of arguments to 1671 .Cr ls (1), 1672 whereas 1673 .Ds 1674 .Cr "fn ls { ls -FC $* } # WRONG" 1675 .De 1676 .TP 1677 \& 1678 is a non-terminating recursion, which will cause 1679 .Cr rc 1680 to exhaust its stack space and (eventually) terminate if it is executed. 1681 .TP 1682 \fBcd \fR[\fIdirectory\fR] 1683 Changes the current directory to 1684 .IR directory . 1685 The variable 1686 .Cr $cdpath 1687 is searched for possible locations of 1688 .IR directory , 1689 analogous to the searching of 1690 .Cr $path 1691 for executable files. 1692 With no argument, 1693 .B cd 1694 changes the current directory to 1695 .Cr "$home" . 1696 .TP 1697 .B continue 1698 Continues the innermost 1699 .Cr for 1700 or 1701 .Cr while 1702 loop, 1703 as in C. 1704 It is an error to invoke 1705 .B continue 1706 outside of a loop. 1707 .TP 1708 \fBecho \fR[\fB\-n\fR] [\fB\-\|\-\fR] [\fIarg ...\fR] 1709 Prints its arguments to standard output, terminated by a newline. 1710 Arguments are separated by spaces. 1711 If the first argument is 1712 .Cr "\-n" 1713 no final newline is printed. 1714 If the first argument is 1715 .Cr "\-\|\-" , 1716 then all other arguments are echoed literally. 1717 This is used for echoing a literal 1718 .Cr "\-n" . 1719 .TP 1720 \fBeval \fR[\fIlist\fR] 1721 Concatenates the elements of 1722 .I list 1723 with spaces and feeds the resulting string to 1724 .I rc 1725 for re-scanning. 1726 This is the only time input is rescanned in 1727 .IR rc . 1728 .TP 1729 \fBexec \fR[\fIarg ...\fR] 1730 Replaces 1731 .I rc 1732 with the given command. 1733 If the exec contains only redirections, 1734 then these redirections apply to the current shell 1735 and the shell does not exit. 1736 For example, 1737 .Ds 1738 .Cr "exec >[2] err.out" 1739 .De 1740 .TP 1741 \& 1742 places further output to standard error in the file 1743 .IR err.out . 1744 .TP 1745 \fBexit \fR[\fIstatus\fR] 1746 Cause the current shell to exit with the given exit 1747 .IR status . 1748 If no argument is given, the current value of 1749 .Cr $status 1750 is used. 1751 .TP 1752 \fBflag\fR \fIf\fR [ \fB+\fR | \fB\-\fR ] 1753 Test, set (\fB+\fR), or reset (\fB\-\fR) command-line flag 1754 .IR f . 1755 For example, a script that requires ``exit if command fails'' semantics can say 1756 .Ds 1757 .Cr "flag e +" 1758 .De 1759 .TP 1760 \& 1761 Some flags cannot be set or reset using 1762 .BR flag , 1763 but they can still be tested. These are 1764 .BR c , 1765 .BR d , 1766 .BR l , 1767 .BR o , 1768 .BR p , 1769 and 1770 .BR s . 1771 As a special case, 1772 .Cr "flag i" 1773 operates on 1774 .BR rc 's 1775 internal 1776 .IR interactive 1777 flag, which may have been set by 1778 .Cr -i 1779 on the command line, or if standard input was a terminal; there is no 1780 .Cr "flag I" . 1781 .TP 1782 \fBlimit \fR[\fB\-h\fR] [\fIresource \fR[\fIvalue\fR]] 1783 Similar to the 1784 .IR csh (1) 1785 .B limit 1786 builtin, this command operates upon the 1787 BSD-style resource limits of a process. 1788 The 1789 .Cr \-h 1790 flag displays/alters the hard 1791 limits. 1792 The resources which can be shown or altered are 1793 .BR cputime , 1794 .BR filesize , 1795 .BR datasize , 1796 .BR stacksize , 1797 .BR coredumpsize , 1798 .BR memoryuse , 1799 and, where supported, 1800 .BR descriptors , 1801 .BR memoryuse , 1802 .BR memoryrss , 1803 .BR maxproc , 1804 .BR memorylocked , 1805 and 1806 .BR filelocks . 1807 For example: 1808 .Ds 1809 .Cr "limit coredumpsize 0" 1810 .De 1811 .TP 1812 \& 1813 disables core dumps. 1814 To set a soft limit equal to the hard limit: 1815 .Ds 1816 .Cr "limit `{limit -h datasize}" 1817 .De 1818 .TP 1819 .B newpgrp 1820 Puts 1821 .I rc 1822 into a new process group. 1823 This builtin is useful for making 1824 .I rc 1825 behave like a job-control shell in a hostile environment. 1826 One example is the NeXT Terminal program, which implicitly assumes 1827 that each shell it forks will put itself into a new process group. 1828 .TP 1829 \fBreturn \fR[\fIn\fR] 1830 Returns from the current function, with status 1831 .IR n , 1832 where 1833 .IR n 1834 is a valid exit status, or a list of them. 1835 Thus it is legal to have 1836 .Ds 1837 .Cr "return (sigpipe 1 2 3)" 1838 .De 1839 .TP 1840 \& 1841 (This is commonly used to allow a function to return with the exit status 1842 of a previously executed pipeline of commands.) 1843 If 1844 .IR n 1845 is omitted, then 1846 .Cr $status 1847 is left unchanged. 1848 It is an error to invoke 1849 .B return 1850 when not inside a function. 1851 .TP 1852 \fBshift \fR[\fIn\fR] 1853 Deletes 1854 .I n 1855 elements from the beginning of 1856 .Cr $* 1857 and shifts the other 1858 elements down by 1859 .IR n . 1860 .I n 1861 defaults to 1. 1862 .TP 1863 \fBumask \fR[\fImask\fR] 1864 Sets the current umask (see 1865 .IR umask (2)) 1866 to the octal 1867 .IR mask . 1868 If no argument is present, the current mask value is printed. 1869 .TP 1870 \fBwait \fR[\fIpid\fR] 1871 Waits for process with the specified 1872 .IR pid , 1873 which must have been started by 1874 .IR rc , 1875 to exit. 1876 If no 1877 .I pid 1878 is specified, 1879 .I rc 1880 waits for all its child processes to exit. 1881 .TP 1882 \fBwhatis \fR[\fB\-b\fR] \fR[\fB\-f\fR] \fR[\fB\-p\fR] \fR[\fB\-s\fR] \fR[\fB\-v\fR] [\fB\-\|\-\fR] [\fIname ...\fR] 1883 Prints a definition of the named objects. 1884 For builtins, 1885 .Cr builtin 1886 .I foo 1887 is printed; for functions, including signal handlers, their definitions 1888 are printed; for executable files, path names are printed; and for 1889 variables, their values are printed. 1890 The flags restrict output to builtins, functions, executable 1891 programs, signal handlers, and variables, respectively. 1892 If no 1893 .IR name s 1894 are specified, 1895 .I rc 1896 lists all objects of that type. 1897 (This is not permitted for 1898 .Cr \-p .) 1899 Without arguments, 1900 .Cr whatis 1901 is equivalent to 1902 .Cr "whatis -fv" , 1903 and prints the values of all shell variables and functions. 1904 .TP 1905 \& 1906 Note that 1907 .B whatis 1908 output is suitable for input to 1909 .IR rc ; 1910 by saving the output of 1911 .B whatis 1912 in a file, it should be possible to recreate the state of 1913 .I rc 1914 by sourcing this file with a 1915 .Cr . 1916 command. 1917 Another note: 1918 .Cr "whatis -s > file" 1919 cannot be used to store the state of 1920 .IR rc 's 1921 signal handlers in a file, because builtins with redirections 1922 are run in a subshell, and 1923 .I rc 1924 always restores signal handlers to their default value after a 1925 .Cr fork() . 1926 .TP 1927 \& 1928 Since 1929 .B whatis 1930 uses 1931 .IR getopt (3) 1932 to parse its arguments, you can use the special argument 1933 .Cr "\-\|\-" 1934 to terminate its flags. 1935 This allows you to use names beginning with a dash, such as 1936 the 1937 .IR history (1) 1938 commands. 1939 For example, 1940 .Ds 1941 .Cr "whatis \-\|\- \-p" 1942 .De 1943 .SH EXAMPLES 1944 The 1945 .B shift 1946 builtin only shifts 1947 .Cr "$*" . 1948 This function can shift any variable (except 1949 .Cr "$_lshift" ). 1950 .Ds 1951 .Cr "fn lshift { _lshift=$* *=$$1 { shift $_lshift(2); $_lshift(1)=$* } }" 1952 .De 1953 .PP 1954 With this definition in place, 1955 .Ds 1956 .Cr "walrus = (shoes ships sealing-wax cabbages kings)" 1957 .Cr "lshift walrus 3" 1958 .Cr "whatis walrus" 1959 .De 1960 .PP 1961 prints 1962 .Ds 1963 .Cr "walrus=(cabbages kings)" 1964 .De 1965 .PP 1966 The 1967 .Cr $^var 1968 operator flattens a list by separating each element with a space. 1969 This function allows the separator to be an arbitrary string. 1970 .Ds 1971 .Cr "fn lflat {" 1972 .Cr " lflat=$*; *=$$1" 1973 .Cr " while () {" 1974 .Cr " echo -n $1; shift" 1975 .Cr " ~ $#* 0 && break" 1976 .Cr " echo -n $lflat(2)" 1977 .Cr " }" 1978 .Cr "}" 1979 .De 1980 .PP 1981 With this definition in place, 1982 .Ds 1983 .Cr "hops=(uunet mcvax ukc tlg)" 1984 .Cr "lflat hops !" 1985 .De 1986 .PP 1987 prints (with no final newline) 1988 .Ds 1989 .Cr uunet!mcvax!ukc!tlg 1990 .De 1991 .SH "EXIT STATUS" 1992 The exit status of 1993 .I rc 1994 is normally the same as that of the last command executed. 1995 If the 1996 last command was a pipeline, 1997 .I rc 1998 exits 1999 .Cr 0 2000 if every command in the pipeline did; otherwise it exits 2001 .Cr 1 . 2002 .PP 2003 .I rc 2004 can be made to exit with a particular status using the 2005 .B exit 2006 builtin. 2007 .SH "LINE EDITING" 2008 .I rc 2009 is typically built against a line editing library. 2010 On GNU/Linux systems this will usually be the GNU 2011 .I readline 2012 library. 2013 On *BSD systems it is more likely to be the BSD 2014 .I editline 2015 library. 2016 Please consult the appropriate library documentation for details of how to use 2017 and configure line editing. 2018 .SS "Tilde Expansion" 2019 Since 2020 .I rc 2021 does not support tilde expansion (converting 2022 .Cr ~foo 2023 to the home directory of user 2024 .Cr foo ), 2025 it is sometimes suggested by users as a 2026 possible enhancement. 2027 The authors and maintainers of 2028 .I rc 2029 have a proud history of resisting such feature requests. 2030 So it is worth noting here that GNU 2031 .I readline 2032 can expand tildes. 2033 Add this line to the file 2034 .Cr .inputrc 2035 in your home directory. 2036 .Ds 2037 .Cr "set expand-tilde on" 2038 .De 2039 .PP 2040 and then use the key sequence 2041 .Cr "M-~" 2042 to perform tilde expansion on the current word. 2043 See the 2044 .I readline 2045 documentation for further details. 2046 .SH GRAMMAR 2047 Here is 2048 .IR rc 's 2049 grammar, edited to remove semantic actions. 2050 .Ds 2051 .ft \*(Cf 2052 %term ANDAND BACKBACK BANG CASE COUNT DUP ELSE END FLAT FN FOR IF IN 2053 %term OROR PIPE REDIR SUB SUBSHELL SWITCH TWIDDLE WHILE WORD HUH 2054 2055 %left '^' '=' 2056 %left WHILE ')' ELSE 2057 %left ANDAND OROR '\en' 2058 %left BANG SUBSHELL 2059 %left PIPE 2060 %right '$' 2061 %left SUB 2062 2063 %start rc 2064 2065 %% 2066 2067 rc: line end 2068 | error end 2069 2070 end: END /* EOF */ | '\en' 2071 2072 cmdsa: cmd ';' | cmd '&' 2073 2074 line: cmd | cmdsa line 2075 2076 body: cmd | cmdsan body 2077 2078 cmdsan: cmdsa | cmd '\en' 2079 2080 brace: '{' body '}' 2081 2082 paren: '(' body ')' 2083 2084 assign: first optcaret '=' optcaret word 2085 2086 epilog: /* empty */ | redir epilog 2087 2088 redir: DUP | REDIR word 2089 2090 case: CASE words ';' | CASE words '\en' 2091 2092 cbody: cmd | case cbody | cmdsan cbody 2093 2094 iftail: cmd %prec ELSE 2095 | brace ELSE optnl cmd 2096 2097 cmd : /* empty */ %prec WHILE 2098 | simple 2099 | brace epilog 2100 | IF paren optnl iftail 2101 | FOR '(' word IN words ')' optnl cmd 2102 | FOR '(' word ')' optnl cmd 2103 | WHILE paren optnl cmd 2104 | SWITCH '(' word ')' optnl '{' cbody '}' 2105 | TWIDDLE optcaret word words 2106 | cmd ANDAND optnl cmd 2107 | cmd OROR optnl cmd 2108 | cmd PIPE optnl cmd 2109 | redir cmd %prec BANG 2110 | assign cmd %prec BANG 2111 | BANG optcaret cmd 2112 | SUBSHELL optcaret cmd 2113 | FN words brace 2114 | FN words 2115 2116 optcaret: /* empty */ %prec '^' | '^' 2117 2118 simple: first | first args 2119 2120 args: arg | args arg 2121 2122 arg: word | redir 2123 2124 first: comword | first '^' sword 2125 2126 sword: comword | keyword 2127 2128 word: sword | word '^' sword 2129 2130 comword: '$' sword 2131 | '$' sword SUB words ')' 2132 | COUNT sword 2133 | FLAT sword 2134 | '`' sword 2135 | '`' brace 2136 | BACKBACK word brace | BACKBACK word sword 2137 | '(' words ')' 2138 | REDIR brace 2139 | WORD 2140 2141 keyword: FOR | IN | WHILE | IF | SWITCH 2142 | FN | ELSE | CASE | TWIDDLE | BANG | SUBSHELL | '=' 2143 2144 words: /* empty */ | words word 2145 2146 optnl: /* empty */ | optnl '\en' 2147 .ft R 2148 .De 2149 .SH FILES 2150 .Cr $HOME/.rcrc , 2151 .Cr /tmp/rc* , 2152 .Cr /dev/null 2153 .SH CREDITS 2154 .I rc 2155 was written by Byron Rakitzis, with valuable help 2156 from Paul Haahr, Hugh Redelmeier and David Sanderson. 2157 The design of this shell was copied from the 2158 .I rc 2159 that Tom Duff wrote at Bell Labs. 2160 .SH BUGS 2161 There is a compile-time limit on the number of 2162 .Cr ; 2163 separated commands in a line: usually 500. 2164 This is sometimes a problem for automatically generated scripts: 2165 substituting the newline character for 2166 .Cr ; 2167 avoids the limit. 2168 .PP 2169 On modern systems that support 2170 .Cr /dev/fd 2171 or 2172 .Cr /proc/self/fd , 2173 .Cr <{foo} 2174 style redirection is implemented that way. 2175 However, on older systems it is implemented with named pipes. 2176 Allegedly, it is sometimes possible to foil 2177 .I rc 2178 into removing the FIFO it places in 2179 .Cr /tmp 2180 prematurely, or it is even possible to cause 2181 .I rc 2182 to hang. 2183 (The current maintainer has never seen this, but then he 2184 doesn't use systems which lack 2185 .Cr /dev/fd 2186 any more. 2187 If anybody can reproduce this problem, please let the maintainer know.) 2188 .PP 2189 The 2190 .B echo 2191 command does not need to be a builtin. It is one for reasons of 2192 performance and portability (of 2193 .I rc 2194 scripts). 2195 .PP 2196 There should be a way to avoid exporting a variable. 2197 .PP 2198 Extra parentheses around a 2199 .Cr ~ 2200 expression or a 2201 .Cr ! 2202 expression are a syntax error. 2203 Thus, this code is illegal. 2204 .Ds 2205 .Cr "while ((~ $1 -*) && (! ~ $1 --)) { ..." 2206 .De 2207 .TP 2208 The redundant inner parentheses must be omitted. 2209 .PP 2210 Variable subscripting cannot be used in here documents. 2211 .PP 2212 The 2213 .Cr limit 2214 builtin silently ignores extra arguments. 2215 .PP 2216 Backquote substitution never produces empty strings - multiple 2217 consecutive occurrences of the separator are treated the same as a 2218 single occurrence. 2219 .Ds 2220 .Cr "ifs=! { x = `{echo -n a!!b}; whatis x }" 2221 .Cr "x=(a b) # NOT x=(a '' b)" 2222 .PP 2223 Bug reports should be mailed to 2224 .Cr "<toby@paccrat.org>" . 2225 .SH INCOMPATIBILITIES 2226 Here is a list of features which distinguish this incarnation of 2227 .I rc 2228 from the one described in the Bell Labs manual pages: 2229 .PP 2230 The Tenth Edition 2231 .I rc 2232 does not have the 2233 .B else 2234 keyword. 2235 Instead, 2236 .B if 2237 is optionally followed by 2238 an 2239 .B "if not" 2240 clause which is executed 2241 if the preceding 2242 .B if 2243 test does not succeed. 2244 .PP 2245 Backquotes are slightly different in Tenth Edition 2246 .IR rc : 2247 a backquote must always be followed by a left-brace. 2248 This restriction is not present for single-word commands in this 2249 .IR rc . 2250 .PP 2251 For 2252 .Cr . 2253 .IR file , 2254 the Tenth Edition 2255 .IR rc 2256 searches 2257 .Cr $path 2258 for 2259 .IR file . 2260 This 2261 .I rc 2262 does not, since it is not considered useful. 2263 .PP 2264 The list flattening operator, 2265 .Cr $^foo , 2266 is spelt 2267 .Cr "$""foo" 2268 in those versions of the Bell Labs 2269 .IR rc 2270 which have it. 2271 .PP 2272 The following are all new with this version of 2273 .IR rc : 2274 The 2275 .Cr \-n 2276 flag, 2277 here strings (they facilitate exporting of functions 2278 with here documents into the environment), 2279 the 2280 .B return 2281 and 2282 .B break 2283 keywords, 2284 the 2285 .B echo 2286 builtin, 2287 the 2288 .Cr bqstatus 2289 and 2290 .Cr version 2291 variables, 2292 the 2293 .Cr prompt 2294 function, 2295 support for GNU 2296 .IR readline 2297 and other line editing libraries. 2298 This 2299 .I rc 2300 also sets 2301 .Cr $0 2302 to the name of a function being executed/file 2303 being sourced. 2304 .SH "SEE ALSO" 2305 ``rc \(em A Shell for Plan 9 and UNIX Systems'', 2306 Unix Research System, 2307 Tenth Edition, 2308 Volume 2. (Saunders College Publishing) 2309 .PP 2310 .Cr http://static.tobold.org/rc/rc-duff.html , 2311 an updated version of the above paper. 2312 .PP 2313 .IR history (1)