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1 | ''' Beginning of part 3 |
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2 | ''' $Header: perl.man.3,v 3.0.1.2 89/11/17 15:31:05 lwall Locked $ |
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3 | ''' |
4 | ''' $Log: perl.man.3,v $ |
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5 | ''' Revision 3.0.1.2 89/11/17 15:31:05 lwall |
6 | ''' patch5: fixed some manual typos and indent problems |
7 | ''' patch5: added warning about print making an array context |
8 | ''' |
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9 | ''' Revision 3.0.1.1 89/11/11 04:45:06 lwall |
10 | ''' patch2: made some line breaks depend on troff vs. nroff |
11 | ''' |
a687059c |
12 | ''' Revision 3.0 89/10/18 15:21:46 lwall |
13 | ''' 3.0 baseline |
14 | ''' |
15 | .Ip "next LABEL" 8 8 |
16 | .Ip "next" 8 |
17 | The |
18 | .I next |
19 | command is like the |
20 | .I continue |
21 | statement in C; it starts the next iteration of the loop: |
22 | .nf |
23 | |
24 | .ne 4 |
25 | line: while (<STDIN>) { |
26 | next line if /\|^#/; # discard comments |
27 | .\|.\|. |
28 | } |
29 | |
30 | .fi |
31 | Note that if there were a |
32 | .I continue |
33 | block on the above, it would get executed even on discarded lines. |
34 | If the LABEL is omitted, the command refers to the innermost enclosing loop. |
35 | .Ip "oct(EXPR)" 8 4 |
36 | .Ip "oct EXPR" 8 |
37 | Returns the decimal value of EXPR interpreted as an octal string. |
38 | (If EXPR happens to start off with 0x, interprets it as a hex string instead.) |
39 | The following will handle decimal, octal and hex in the standard notation: |
40 | .nf |
41 | |
42 | $val = oct($val) if $val =~ /^0/; |
43 | |
44 | .fi |
45 | If EXPR is omitted, uses $_. |
46 | .Ip "open(FILEHANDLE,EXPR)" 8 8 |
47 | .Ip "open(FILEHANDLE)" 8 |
48 | .Ip "open FILEHANDLE" 8 |
49 | Opens the file whose filename is given by EXPR, and associates it with |
50 | FILEHANDLE. |
51 | If FILEHANDLE is an expression, its value is used as the name of the |
52 | real filehandle wanted. |
53 | If EXPR is omitted, the scalar variable of the same name as the FILEHANDLE |
54 | contains the filename. |
55 | If the filename begins with \*(L"<\*(R" or nothing, the file is opened for |
56 | input. |
57 | If the filename begins with \*(L">\*(R", the file is opened for output. |
58 | If the filename begins with \*(L">>\*(R", the file is opened for appending. |
59 | (You can put a \'+\' in front of the \'>\' or \'<\' to indicate that you |
60 | want both read and write access to the file.) |
61 | If the filename begins with \*(L"|\*(R", the filename is interpreted |
62 | as a command to which output is to be piped, and if the filename ends |
63 | with a \*(L"|\*(R", the filename is interpreted as command which pipes |
64 | input to us. |
65 | (You may not have a command that pipes both in and out.) |
66 | Opening \'\-\' opens |
67 | .I STDIN |
68 | and opening \'>\-\' opens |
69 | .IR STDOUT . |
70 | Open returns non-zero upon success, the undefined value otherwise. |
71 | If the open involved a pipe, the return value happens to be the pid |
72 | of the subprocess. |
73 | Examples: |
74 | .nf |
75 | |
76 | .ne 3 |
77 | $article = 100; |
78 | open article || die "Can't find article $article: $!\en"; |
79 | while (<article>) {\|.\|.\|. |
80 | |
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81 | .ie t \{\ |
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82 | open(LOG, \'>>/usr/spool/news/twitlog\'\|); # (log is reserved) |
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83 | 'br\} |
84 | .el \{\ |
85 | open(LOG, \'>>/usr/spool/news/twitlog\'\|); |
86 | # (log is reserved) |
87 | 'br\} |
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88 | |
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89 | .ie t \{\ |
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90 | open(article, "caesar <$article |"\|); # decrypt article |
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91 | 'br\} |
92 | .el \{\ |
93 | open(article, "caesar <$article |"\|); |
94 | # decrypt article |
95 | 'br\} |
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96 | |
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97 | .ie t \{\ |
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98 | open(extract, "|sort >/tmp/Tmp$$"\|); # $$ is our process# |
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99 | 'br\} |
100 | .el \{\ |
101 | open(extract, "|sort >/tmp/Tmp$$"\|); |
102 | # $$ is our process# |
103 | 'br\} |
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104 | |
105 | .ne 7 |
106 | # process argument list of files along with any includes |
107 | |
108 | foreach $file (@ARGV) { |
109 | do process($file, \'fh00\'); # no pun intended |
110 | } |
111 | |
112 | sub process { |
113 | local($filename, $input) = @_; |
114 | $input++; # this is a string increment |
115 | unless (open($input, $filename)) { |
116 | print STDERR "Can't open $filename: $!\en"; |
117 | return; |
118 | } |
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119 | .ie t \{\ |
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120 | while (<$input>) { # note the use of indirection |
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121 | 'br\} |
122 | .el \{\ |
123 | while (<$input>) { # note use of indirection |
124 | 'br\} |
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125 | if (/^#include "(.*)"/) { |
126 | do process($1, $input); |
127 | next; |
128 | } |
129 | .\|.\|. # whatever |
130 | } |
131 | } |
132 | |
133 | .fi |
134 | You may also, in the Bourne shell tradition, specify an EXPR beginning |
135 | with \*(L">&\*(R", in which case the rest of the string |
136 | is interpreted as the name of a filehandle |
137 | (or file descriptor, if numeric) which is to be duped and opened. |
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138 | You may use & after >, >>, <, +>, +>> and +<. |
139 | The mode you specify should match the mode of the original filehandle. |
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140 | Here is a script that saves, redirects, and restores |
141 | .I STDOUT |
142 | and |
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143 | .IR STDERR : |
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144 | .nf |
145 | |
146 | .ne 21 |
147 | #!/usr/bin/perl |
148 | open(SAVEOUT, ">&STDOUT"); |
149 | open(SAVEERR, ">&STDERR"); |
150 | |
151 | open(STDOUT, ">foo.out") || die "Can't redirect stdout"; |
152 | open(STDERR, ">&STDOUT") || die "Can't dup stdout"; |
153 | |
154 | select(STDERR); $| = 1; # make unbuffered |
155 | select(STDOUT); $| = 1; # make unbuffered |
156 | |
157 | print STDOUT "stdout 1\en"; # this works for |
158 | print STDERR "stderr 1\en"; # subprocesses too |
159 | |
160 | close(STDOUT); |
161 | close(STDERR); |
162 | |
163 | open(STDOUT, ">&SAVEOUT"); |
164 | open(STDERR, ">&SAVEERR"); |
165 | |
166 | print STDOUT "stdout 2\en"; |
167 | print STDERR "stderr 2\en"; |
168 | |
169 | .fi |
170 | If you open a pipe on the command \*(L"\-\*(R", i.e. either \*(L"|\-\*(R" or \*(L"\-|\*(R", |
171 | then there is an implicit fork done, and the return value of open |
172 | is the pid of the child within the parent process, and 0 within the child |
173 | process. |
174 | (Use defined($pid) to determine if the open was successful.) |
175 | The filehandle behaves normally for the parent, but i/o to that |
176 | filehandle is piped from/to the |
177 | .IR STDOUT / STDIN |
178 | of the child process. |
179 | In the child process the filehandle isn't opened\*(--i/o happens from/to |
180 | the new |
181 | .I STDOUT |
182 | or |
183 | .IR STDIN . |
184 | Typically this is used like the normal piped open when you want to exercise |
185 | more control over just how the pipe command gets executed, such as when |
186 | you are running setuid, and don't want to have to scan shell commands |
187 | for metacharacters. |
188 | The following pairs are equivalent: |
189 | .nf |
190 | |
191 | .ne 5 |
192 | open(FOO, "|tr \'[a\-z]\' \'[A\-Z]\'"); |
193 | open(FOO, "|\-") || exec \'tr\', \'[a\-z]\', \'[A\-Z]\'; |
194 | |
195 | open(FOO, "cat \-n $file|"); |
196 | open(FOO, "\-|") || exec \'cat\', \'\-n\', $file; |
197 | |
198 | .fi |
199 | Explicitly closing any piped filehandle causes the parent process to wait for the |
200 | child to finish, and returns the status value in $?. |
201 | .Ip "opendir(DIRHANDLE,EXPR)" 8 3 |
202 | Opens a directory named EXPR for processing by readdir(), telldir(), seekdir(), |
203 | rewinddir() and closedir(). |
204 | Returns true if successful. |
205 | DIRHANDLEs have their own namespace separate from FILEHANDLEs. |
206 | .Ip "ord(EXPR)" 8 4 |
207 | .Ip "ord EXPR" 8 |
208 | Returns the ascii value of the first character of EXPR. |
209 | If EXPR is omitted, uses $_. |
210 | .Ip "pack(TEMPLATE,LIST)" 8 4 |
211 | Takes an array or list of values and packs it into a binary structure, |
212 | returning the string containing the structure. |
213 | The TEMPLATE is a sequence of characters that give the order and type |
214 | of values, as follows: |
215 | .nf |
216 | |
217 | A An ascii string, will be space padded. |
218 | a An ascii string, will be null padded. |
219 | c A native char value. |
220 | C An unsigned char value. |
221 | s A signed short value. |
222 | S An unsigned short value. |
223 | i A signed integer value. |
224 | I An unsigned integer value. |
225 | l A signed long value. |
226 | L An unsigned long value. |
227 | n A short in \*(L"network\*(R" order. |
228 | N A long in \*(L"network\*(R" order. |
229 | p A pointer to a string. |
230 | x A null byte. |
231 | |
232 | .fi |
233 | Each letter may optionally be followed by a number which gives a repeat |
234 | count. |
235 | With all types except "a" and "A" the pack function will gobble up that many values |
236 | from the LIST. |
237 | The "a" and "A" types gobble just one value, but pack it as a string that long, |
238 | padding with nulls or spaces as necessary. |
239 | (When unpacking, "A" strips trailing spaces and nulls, but "a" does not.) |
240 | Examples: |
241 | .nf |
242 | |
243 | $foo = pack("cccc",65,66,67,68); |
244 | # foo eq "ABCD" |
245 | $foo = pack("c4",65,66,67,68); |
246 | # same thing |
247 | |
248 | $foo = pack("ccxxcc",65,66,67,68); |
249 | # foo eq "AB\e0\e0CD" |
250 | |
251 | $foo = pack("s2",1,2); |
252 | # "\e1\e0\e2\e0" on little-endian |
253 | # "\e0\e1\e0\e2" on big-endian |
254 | |
255 | $foo = pack("a4","abcd","x","y","z"); |
256 | # "abcd" |
257 | |
258 | $foo = pack("aaaa","abcd","x","y","z"); |
259 | # "axyz" |
260 | |
261 | $foo = pack("a14","abcdefg"); |
262 | # "abcdefg\e0\e0\e0\e0\e0\e0\e0" |
263 | |
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264 | $foo = pack("i9pl", gmtime); |
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265 | # a real struct tm (on my system anyway) |
266 | |
267 | .fi |
268 | The same template may generally also be used in the unpack function. |
269 | .Ip "pop(ARRAY)" 8 |
270 | .Ip "pop ARRAY" 8 6 |
271 | Pops and returns the last value of the array, shortening the array by 1. |
272 | Has the same effect as |
273 | .nf |
274 | |
275 | $tmp = $ARRAY[$#ARRAY\-\|\-]; |
276 | |
277 | .fi |
278 | If there are no elements in the array, returns the undefined value. |
279 | .Ip "print(FILEHANDLE LIST)" 8 10 |
280 | .Ip "print(LIST)" 8 |
281 | .Ip "print FILEHANDLE LIST" 8 |
282 | .Ip "print LIST" 8 |
283 | .Ip "print" 8 |
284 | Prints a string or a comma-separated list of strings. |
285 | Returns non-zero if successful. |
286 | FILEHANDLE may be a scalar variable name, in which case the variable contains |
287 | the name of the filehandle, thus introducing one level of indirection. |
288 | If FILEHANDLE is omitted, prints by default to standard output (or to the |
289 | last selected output channel\*(--see select()). |
290 | If LIST is also omitted, prints $_ to |
291 | .IR STDOUT . |
292 | To set the default output channel to something other than |
293 | .I STDOUT |
294 | use the select operation. |
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295 | Note that, because print takes a LIST, anything in the LIST is evaluated |
296 | in an array context, and any subroutine that you call will have one or more |
297 | of its expressions evaluated in an array context. |
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298 | .Ip "printf(FILEHANDLE LIST)" 8 10 |
299 | .Ip "printf(LIST)" 8 |
300 | .Ip "printf FILEHANDLE LIST" 8 |
301 | .Ip "printf LIST" 8 |
302 | Equivalent to a \*(L"print FILEHANDLE sprintf(LIST)\*(R". |
303 | .Ip "push(ARRAY,LIST)" 8 7 |
304 | Treats ARRAY (@ is optional) as a stack, and pushes the values of LIST |
305 | onto the end of ARRAY. |
306 | The length of ARRAY increases by the length of LIST. |
307 | Has the same effect as |
308 | .nf |
309 | |
310 | for $value (LIST) { |
311 | $ARRAY[++$#ARRAY] = $value; |
312 | } |
313 | |
314 | .fi |
315 | but is more efficient. |
316 | .Ip "q/STRING/" 8 5 |
317 | .Ip "qq/STRING/" 8 |
318 | These are not really functions, but simply syntactic sugar to let you |
319 | avoid putting too many backslashes into quoted strings. |
320 | The q operator is a generalized single quote, and the qq operator a |
321 | generalized double quote. |
322 | Any delimiter can be used in place of /, including newline. |
323 | If the delimiter is an opening bracket or parenthesis, the final delimiter |
324 | will be the corresponding closing bracket or parenthesis. |
325 | (Embedded occurrences of the closing bracket need to be backslashed as usual.) |
326 | Examples: |
327 | .nf |
328 | |
329 | .ne 5 |
330 | $foo = q!I said, "You said, \'She said it.\'"!; |
331 | $bar = q(\'This is it.\'); |
332 | $_ .= qq |
333 | *** The previous line contains the naughty word "$&".\en |
334 | if /(ibm|apple|awk)/; # :-) |
335 | |
336 | .fi |
337 | .Ip "rand(EXPR)" 8 8 |
338 | .Ip "rand EXPR" 8 |
339 | .Ip "rand" 8 |
340 | Returns a random fractional number between 0 and the value of EXPR. |
341 | (EXPR should be positive.) |
342 | If EXPR is omitted, returns a value between 0 and 1. |
343 | See also srand(). |
344 | .Ip "read(FILEHANDLE,SCALAR,LENGTH)" 8 5 |
345 | Attempts to read LENGTH bytes of data into variable SCALAR from the specified |
346 | FILEHANDLE. |
347 | Returns the number of bytes actually read. |
348 | SCALAR will be grown or shrunk to the length actually read. |
349 | .Ip "readdir(DIRHANDLE)" 8 3 |
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350 | .Ip "readdir DIRHANDLE" 8 |
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351 | Returns the next directory entry for a directory opened by opendir(). |
352 | If used in an array context, returns all the rest of the entries in the |
353 | directory. |
354 | If there are no more entries, returns an undefined value in a scalar context |
355 | or a null list in an array context. |
356 | .Ip "readlink(EXPR)" 8 6 |
357 | .Ip "readlink EXPR" 8 |
358 | Returns the value of a symbolic link, if symbolic links are implemented. |
359 | If not, gives a fatal error. |
360 | If there is some system error, returns the undefined value and sets $! (errno). |
361 | If EXPR is omitted, uses $_. |
362 | .Ip "recv(SOCKET,SCALAR,LEN,FLAGS)" 8 4 |
363 | Receives a message on a socket. |
364 | Attempts to receive LENGTH bytes of data into variable SCALAR from the specified |
365 | SOCKET filehandle. |
366 | Returns the address of the sender, or the undefined value if there's an error. |
367 | SCALAR will be grown or shrunk to the length actually read. |
368 | Takes the same flags as the system call of the same name. |
369 | .Ip "redo LABEL" 8 8 |
370 | .Ip "redo" 8 |
371 | The |
372 | .I redo |
373 | command restarts the loop block without evaluating the conditional again. |
374 | The |
375 | .I continue |
376 | block, if any, is not executed. |
377 | If the LABEL is omitted, the command refers to the innermost enclosing loop. |
378 | This command is normally used by programs that want to lie to themselves |
379 | about what was just input: |
380 | .nf |
381 | |
382 | .ne 16 |
383 | # a simpleminded Pascal comment stripper |
384 | # (warning: assumes no { or } in strings) |
385 | line: while (<STDIN>) { |
386 | while (s|\|({.*}.*\|){.*}|$1 \||) {} |
387 | s|{.*}| \||; |
388 | if (s|{.*| \||) { |
389 | $front = $_; |
390 | while (<STDIN>) { |
391 | if (\|/\|}/\|) { # end of comment? |
392 | s|^|$front{|; |
393 | redo line; |
394 | } |
395 | } |
396 | } |
397 | print; |
398 | } |
399 | |
400 | .fi |
401 | .Ip "rename(OLDNAME,NEWNAME)" 8 2 |
402 | Changes the name of a file. |
403 | Returns 1 for success, 0 otherwise. |
404 | Will not work across filesystem boundaries. |
405 | .Ip "reset(EXPR)" 8 6 |
406 | .Ip "reset EXPR" 8 |
407 | .Ip "reset" 8 |
408 | Generally used in a |
409 | .I continue |
410 | block at the end of a loop to clear variables and reset ?? searches |
411 | so that they work again. |
412 | The expression is interpreted as a list of single characters (hyphens allowed |
413 | for ranges). |
414 | All variables and arrays beginning with one of those letters are reset to |
415 | their pristine state. |
416 | If the expression is omitted, one-match searches (?pattern?) are reset to |
417 | match again. |
418 | Only resets variables or searches in the current package. |
419 | Always returns 1. |
420 | Examples: |
421 | .nf |
422 | |
423 | .ne 3 |
424 | reset \'X\'; \h'|2i'# reset all X variables |
425 | reset \'a\-z\';\h'|2i'# reset lower case variables |
426 | reset; \h'|2i'# just reset ?? searches |
427 | |
428 | .fi |
429 | Note: resetting \*(L"A\-Z\*(R" is not recommended since you'll wipe out your ARGV and ENV |
430 | arrays. |
431 | .Sp |
432 | The use of reset on dbm associative arrays does not change the dbm file. |
433 | (It does, however, flush any entries cached by perl, which may be useful if |
434 | you are sharing the dbm file. |
435 | Then again, maybe not.) |
436 | .Ip "return LIST" 8 3 |
437 | Returns from a subroutine with the value specified. |
438 | (Note that a subroutine can automatically return |
439 | the value of the last expression evaluated. |
440 | That's the preferred method\*(--use of an explicit |
441 | .I return |
442 | is a bit slower.) |
443 | .Ip "reverse(LIST)" 8 4 |
444 | .Ip "reverse LIST" 8 |
445 | Returns an array value consisting of the elements of LIST in the opposite order. |
446 | .Ip "rewinddir(DIRHANDLE)" 8 5 |
447 | .Ip "rewinddir DIRHANDLE" 8 |
448 | Sets the current position to the beginning of the directory for the readdir() routine on DIRHANDLE. |
449 | .Ip "rindex(STR,SUBSTR)" 8 4 |
450 | Works just like index except that it |
451 | returns the position of the LAST occurrence of SUBSTR in STR. |
452 | .Ip "rmdir(FILENAME)" 8 4 |
453 | .Ip "rmdir FILENAME" 8 |
454 | Deletes the directory specified by FILENAME if it is empty. |
455 | If it succeeds it returns 1, otherwise it returns 0 and sets $! (errno). |
456 | If FILENAME is omitted, uses $_. |
457 | .Ip "s/PATTERN/REPLACEMENT/gieo" 8 3 |
458 | Searches a string for a pattern, and if found, replaces that pattern with the |
459 | replacement text and returns the number of substitutions made. |
460 | Otherwise it returns false (0). |
461 | The \*(L"g\*(R" is optional, and if present, indicates that all occurrences |
462 | of the pattern are to be replaced. |
463 | The \*(L"i\*(R" is also optional, and if present, indicates that matching |
464 | is to be done in a case-insensitive manner. |
465 | The \*(L"e\*(R" is likewise optional, and if present, indicates that |
466 | the replacement string is to be evaluated as an expression rather than just |
467 | as a double-quoted string. |
468 | Any delimiter may replace the slashes; if single quotes are used, no |
469 | interpretation is done on the replacement string (the e modifier overrides |
470 | this, however). |
471 | If no string is specified via the =~ or !~ operator, |
472 | the $_ string is searched and modified. |
473 | (The string specified with =~ must be a scalar variable, an array element, |
474 | or an assignment to one of those, i.e. an lvalue.) |
475 | If the pattern contains a $ that looks like a variable rather than an |
476 | end-of-string test, the variable will be interpolated into the pattern at |
477 | run-time. |
478 | If you only want the pattern compiled once the first time the variable is |
479 | interpolated, add an \*(L"o\*(R" at the end. |
480 | See also the section on regular expressions. |
481 | Examples: |
482 | .nf |
483 | |
484 | s/\|\e\|bgreen\e\|b/mauve/g; # don't change wintergreen |
485 | |
486 | $path \|=~ \|s|\|/usr/bin|\|/usr/local/bin|; |
487 | |
488 | s/Login: $foo/Login: $bar/; # run-time pattern |
489 | |
490 | ($foo = $bar) =~ s/bar/foo/; |
491 | |
492 | $_ = \'abc123xyz\'; |
493 | s/\ed+/$&*2/e; # yields \*(L'abc246xyz\*(R' |
494 | s/\ed+/sprintf("%5d",$&)/e; # yields \*(L'abc 246xyz\*(R' |
495 | s/\ew/$& x 2/eg; # yields \*(L'aabbcc 224466xxyyzz\*(R' |
496 | |
497 | s/\|([^ \|]*\|) *\|([^ \|]*\|)\|/\|$2 $1/; # reverse 1st two fields |
498 | |
499 | .fi |
500 | (Note the use of $ instead of \|\e\| in the last example. See section |
501 | on regular expressions.) |
502 | .Ip "seek(FILEHANDLE,POSITION,WHENCE)" 8 3 |
503 | Randomly positions the file pointer for FILEHANDLE, just like the fseek() |
504 | call of stdio. |
505 | FILEHANDLE may be an expression whose value gives the name of the filehandle. |
506 | Returns 1 upon success, 0 otherwise. |
507 | .Ip "seekdir(DIRHANDLE,POS)" 8 3 |
508 | Sets the current position for the readdir() routine on DIRHANDLE. |
509 | POS must be a value returned by seekdir(). |
510 | Has the same caveats about possible directory compaction as the corresponding |
511 | system library routine. |
512 | .Ip "select(FILEHANDLE)" 8 3 |
513 | .Ip "select" 8 3 |
514 | Returns the currently selected filehandle. |
515 | Sets the current default filehandle for output, if FILEHANDLE is supplied. |
516 | This has two effects: first, a |
517 | .I write |
518 | or a |
519 | .I print |
520 | without a filehandle will default to this FILEHANDLE. |
521 | Second, references to variables related to output will refer to this output |
522 | channel. |
523 | For example, if you have to set the top of form format for more than |
524 | one output channel, you might do the following: |
525 | .nf |
526 | |
527 | .ne 4 |
528 | select(REPORT1); |
529 | $^ = \'report1_top\'; |
530 | select(REPORT2); |
531 | $^ = \'report2_top\'; |
532 | |
533 | .fi |
534 | FILEHANDLE may be an expression whose value gives the name of the actual filehandle. |
535 | Thus: |
536 | .nf |
537 | |
538 | $oldfh = select(STDERR); $| = 1; select($oldfh); |
539 | |
540 | .fi |
541 | .Ip "select(RBITS,WBITS,EBITS,TIMEOUT)" 8 3 |
542 | This calls the select system call with the bitmasks specified, which can |
543 | be constructed using fileno() and vec(), along these lines: |
544 | .nf |
545 | |
546 | $rin = $win = $ein = ''; |
547 | vec($rin,fileno(STDIN),1) = 1; |
548 | vec($win,fileno(STDOUT),1) = 1; |
549 | $ein = $rin | $win; |
550 | |
551 | .fi |
552 | If you want to select on many filehandles you might wish to write a subroutine: |
553 | .nf |
554 | |
555 | sub fhbits { |
556 | local(@fhlist) = split(' ',$_[0]); |
557 | local($bits); |
558 | for (@fhlist) { |
559 | vec($bits,fileno($_),1) = 1; |
560 | } |
561 | $bits; |
562 | } |
563 | $rin = &fhbits('STDIN TTY SOCK'); |
564 | |
565 | .fi |
566 | The usual idiom is: |
567 | .nf |
568 | |
569 | ($nfound,$timeleft) = |
570 | select($rout=$rin, $wout=$win, $eout=$ein, $timeout); |
571 | |
572 | or to block until something becomes ready: |
573 | |
ae986130 |
574 | .ie t \{\ |
a687059c |
575 | $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef); |
ae986130 |
576 | 'br\} |
577 | .el \{\ |
578 | $nfound = select($rout=$rin, $wout=$win, |
579 | $eout=$ein, undef); |
580 | 'br\} |
a687059c |
581 | |
582 | .fi |
583 | Any of the bitmasks can also be undef. |
584 | The timeout, if specified, is in seconds, which may be fractional. |
585 | .Ip "setpgrp(PID,PGRP)" 8 4 |
586 | Sets the current process group for the specified PID, 0 for the current |
587 | process. |
588 | Will produce a fatal error if used on a machine that doesn't implement |
589 | setpgrp(2). |
590 | .Ip "send(SOCKET,MSG,FLAGS,TO)" 8 4 |
591 | .Ip "send(SOCKET,MSG,FLAGS)" 8 |
592 | Sends a message on a socket. |
593 | Takes the same flags as the system call of the same name. |
594 | On unconnected sockets you must specify a destination to send TO. |
595 | Returns the number of characters sent, or the undefined value if |
596 | there is an error. |
597 | .Ip "setpriority(WHICH,WHO,PRIORITY)" 8 4 |
598 | Sets the current priority for a process, a process group, or a user. |
599 | (See setpriority(2).) |
600 | Will produce a fatal error if used on a machine that doesn't implement |
601 | setpriority(2). |
602 | .Ip "setsockopt(SOCKET,LEVEL,OPTNAME,OPTVAL)" 8 3 |
603 | Sets the socket option requested. |
604 | Returns undefined if there is an error. |
605 | OPTVAL may be specified as undef if you don't want to pass an argument. |
606 | .Ip "shift(ARRAY)" 8 6 |
607 | .Ip "shift ARRAY" 8 |
608 | .Ip "shift" 8 |
609 | Shifts the first value of the array off and returns it, |
610 | shortening the array by 1 and moving everything down. |
611 | If there are no elements in the array, returns the undefined value. |
612 | If ARRAY is omitted, shifts the @ARGV array in the main program, and the @_ |
613 | array in subroutines. |
614 | See also unshift(), push() and pop(). |
615 | Shift() and unshift() do the same thing to the left end of an array that push() |
616 | and pop() do to the right end. |
617 | .Ip "shutdown(SOCKET,HOW)" 8 3 |
618 | Shuts down a socket connection in the manner indicated by HOW, which has |
619 | the same interpretation as in the system call of the same name. |
620 | .Ip "sin(EXPR)" 8 4 |
621 | .Ip "sin EXPR" 8 |
622 | Returns the sine of EXPR (expressed in radians). |
623 | If EXPR is omitted, returns sine of $_. |
624 | .Ip "sleep(EXPR)" 8 6 |
625 | .Ip "sleep EXPR" 8 |
626 | .Ip "sleep" 8 |
627 | Causes the script to sleep for EXPR seconds, or forever if no EXPR. |
628 | May be interrupted by sending the process a SIGALARM. |
629 | Returns the number of seconds actually slept. |
630 | .Ip "socket(SOCKET,DOMAIN,TYPE,PROTOCOL)" 8 3 |
631 | Opens a socket of the specified kind and attaches it to filehandle SOCKET. |
632 | DOMAIN, TYPE and PROTOCOL are specified the same as for the system call |
633 | of the same name. |
634 | You may need to run makelib on sys/socket.h to get the proper values handy |
635 | in a perl library file. |
636 | Return true if successful. |
637 | See the example in the section on Interprocess Communication. |
638 | .Ip "socketpair(SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL)" 8 3 |
639 | Creates an unnamed pair of sockets in the specified domain, of the specified |
640 | type. |
641 | DOMAIN, TYPE and PROTOCOL are specified the same as for the system call |
642 | of the same name. |
643 | If unimplemented, yields a fatal error. |
644 | Return true if successful. |
645 | .Ip "sort(SUBROUTINE LIST)" 8 9 |
646 | .Ip "sort(LIST)" 8 |
647 | .Ip "sort SUBROUTINE LIST" 8 |
648 | .Ip "sort LIST" 8 |
649 | Sorts the LIST and returns the sorted array value. |
650 | Nonexistent values of arrays are stripped out. |
651 | If SUBROUTINE is omitted, sorts in standard string comparison order. |
652 | If SUBROUTINE is specified, gives the name of a subroutine that returns |
653 | an integer less than, equal to, or greater than 0, |
654 | depending on how the elements of the array are to be ordered. |
655 | In the interests of efficiency the normal calling code for subroutines |
656 | is bypassed, with the following effects: the subroutine may not be a recursive |
657 | subroutine, and the two elements to be compared are passed into the subroutine |
658 | not via @_ but as $a and $b (see example below). |
659 | They are passed by reference so don't modify $a and $b. |
660 | SUBROUTINE may be a scalar variable name, in which case the value provides |
661 | the name of the subroutine to use. |
662 | Examples: |
663 | .nf |
664 | |
665 | .ne 4 |
666 | sub byage { |
667 | $age{$a} - $age{$b}; # presuming integers |
668 | } |
669 | @sortedclass = sort byage @class; |
670 | |
671 | .ne 9 |
672 | sub reverse { $a lt $b ? 1 : $a gt $b ? \-1 : 0; } |
673 | @harry = (\'dog\',\'cat\',\'x\',\'Cain\',\'Abel\'); |
674 | @george = (\'gone\',\'chased\',\'yz\',\'Punished\',\'Axed\'); |
675 | print sort @harry; |
676 | # prints AbelCaincatdogx |
677 | print sort reverse @harry; |
678 | # prints xdogcatCainAbel |
679 | print sort @george, \'to\', @harry; |
680 | # prints AbelAxedCainPunishedcatchaseddoggonetoxyz |
681 | |
682 | .fi |
683 | .Ip "split(/PATTERN/,EXPR,LIMIT)" 8 8 |
684 | .Ip "split(/PATTERN/,EXPR)" 8 8 |
685 | .Ip "split(/PATTERN/)" 8 |
686 | .Ip "split" 8 |
687 | Splits a string into an array of strings, and returns it. |
688 | (If not in an array context, returns the number of fields found and splits |
689 | into the @_ array.) |
690 | If EXPR is omitted, splits the $_ string. |
691 | If PATTERN is also omitted, splits on whitespace (/[\ \et\en]+/). |
692 | Anything matching PATTERN is taken to be a delimiter separating the fields. |
693 | (Note that the delimiter may be longer than one character.) |
694 | If LIMIT is specified, splits into no more than that many fields (though it |
695 | may split into fewer). |
696 | If LIMIT is unspecified, trailing null fields are stripped (which |
697 | potential users of pop() would do well to remember). |
698 | A pattern matching the null string (not to be confused with a null pattern, |
699 | which is one member of the set of patterns matching a null string) |
700 | will split the value of EXPR into separate characters at each point it |
701 | matches that way. |
702 | For example: |
703 | .nf |
704 | |
705 | print join(\':\', split(/ */, \'hi there\')); |
706 | |
707 | .fi |
708 | produces the output \*(L'h:i:t:h:e:r:e\*(R'. |
ffed7fef |
709 | .Sp |
a687059c |
710 | The NUM parameter can be used to partially split a line |
711 | .nf |
712 | |
713 | ($login, $passwd, $remainder) = split(\|/\|:\|/\|, $_, 3); |
714 | |
715 | .fi |
716 | (When assigning to a list, if NUM is omitted, perl supplies a NUM one |
717 | larger than the number of variables in the list, to avoid unnecessary work. |
718 | For the list above NUM would have been 4 by default. |
719 | In time critical applications it behooves you not to split into |
720 | more fields than you really need.) |
721 | .Sp |
722 | If the PATTERN contains parentheses, additional array elements are created |
723 | from each matching substring in the delimiter. |
724 | .Sp |
725 | split(/([,-])/,"1-10,20"); |
726 | .Sp |
727 | produces the array value |
728 | .Sp |
729 | (1,'-',10,',',20) |
730 | .Sp |
731 | The pattern /PATTERN/ may be replaced with an expression to specify patterns |
732 | that vary at runtime. |
733 | (To do runtime compilation only once, use /$variable/o.) |
734 | As a special case, specifying a space (\'\ \') will split on white space |
735 | just as split with no arguments does, but leading white space does NOT |
736 | produce a null first field. |
737 | Thus, split(\'\ \') can be used to emulate |
738 | .IR awk 's |
739 | default behavior, whereas |
740 | split(/\ /) will give you as many null initial fields as there are |
741 | leading spaces. |
742 | .Sp |
743 | Example: |
744 | .nf |
745 | |
746 | .ne 5 |
747 | open(passwd, \'/etc/passwd\'); |
748 | while (<passwd>) { |
749 | .ie t \{\ |
750 | ($login, $passwd, $uid, $gid, $gcos, $home, $shell) = split(\|/\|:\|/\|); |
751 | 'br\} |
752 | .el \{\ |
753 | ($login, $passwd, $uid, $gid, $gcos, $home, $shell) |
754 | = split(\|/\|:\|/\|); |
755 | 'br\} |
756 | .\|.\|. |
757 | } |
758 | |
759 | .fi |
760 | (Note that $shell above will still have a newline on it. See chop().) |
761 | See also |
762 | .IR join . |
763 | .Ip "sprintf(FORMAT,LIST)" 8 4 |
764 | Returns a string formatted by the usual printf conventions. |
765 | The * character is not supported. |
766 | .Ip "sqrt(EXPR)" 8 4 |
767 | .Ip "sqrt EXPR" 8 |
768 | Return the square root of EXPR. |
769 | If EXPR is omitted, returns square root of $_. |
770 | .Ip "srand(EXPR)" 8 4 |
771 | .Ip "srand EXPR" 8 |
772 | Sets the random number seed for the |
773 | .I rand |
774 | operator. |
775 | If EXPR is omitted, does srand(time). |
ae986130 |
776 | .Ip "stat(FILEHANDLE)" 8 8 |
a687059c |
777 | .Ip "stat FILEHANDLE" 8 |
778 | .Ip "stat(EXPR)" 8 |
ae986130 |
779 | .Ip "stat SCALARVARIABLE" 8 |
a687059c |
780 | Returns a 13-element array giving the statistics for a file, either the file |
781 | opened via FILEHANDLE, or named by EXPR. |
782 | Typically used as follows: |
783 | .nf |
784 | |
785 | .ne 3 |
786 | ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size, |
787 | $atime,$mtime,$ctime,$blksize,$blocks) |
788 | = stat($filename); |
789 | |
790 | .fi |
791 | If stat is passed the special filehandle consisting of an underline, |
792 | no stat is done, but the current contents of the stat structure from |
793 | the last stat or filetest are returned. |
794 | Example: |
795 | .nf |
796 | |
797 | .ne 3 |
798 | if (-x $file && (($d) = stat(_)) && $d < 0) { |
799 | print "$file is executable NFS file\en"; |
800 | } |
801 | |
802 | .fi |
803 | .Ip "study(SCALAR)" 8 6 |
804 | .Ip "study SCALAR" 8 |
805 | .Ip "study" |
806 | Takes extra time to study SCALAR ($_ if unspecified) in anticipation of |
807 | doing many pattern matches on the string before it is next modified. |
808 | This may or may not save time, depending on the nature and number of patterns |
809 | you are searching on, and on the distribution of character frequencies in |
810 | the string to be searched\*(--you probably want to compare runtimes with and |
811 | without it to see which runs faster. |
812 | Those loops which scan for many short constant strings (including the constant |
813 | parts of more complex patterns) will benefit most. |
814 | You may have only one study active at a time\*(--if you study a different |
815 | scalar the first is \*(L"unstudied\*(R". |
816 | (The way study works is this: a linked list of every character in the string |
817 | to be searched is made, so we know, for example, where all the \*(L'k\*(R' characters |
818 | are. |
819 | From each search string, the rarest character is selected, based on some |
820 | static frequency tables constructed from some C programs and English text. |
821 | Only those places that contain this \*(L"rarest\*(R" character are examined.) |
822 | .Sp |
823 | For example, here is a loop which inserts index producing entries before any line |
824 | containing a certain pattern: |
825 | .nf |
826 | |
827 | .ne 8 |
828 | while (<>) { |
829 | study; |
830 | print ".IX foo\en" if /\ebfoo\eb/; |
831 | print ".IX bar\en" if /\ebbar\eb/; |
832 | print ".IX blurfl\en" if /\ebblurfl\eb/; |
833 | .\|.\|. |
834 | print; |
835 | } |
836 | |
837 | .fi |
838 | In searching for /\ebfoo\eb/, only those locations in $_ that contain \*(L'f\*(R' |
839 | will be looked at, because \*(L'f\*(R' is rarer than \*(L'o\*(R'. |
840 | In general, this is a big win except in pathological cases. |
841 | The only question is whether it saves you more time than it took to build |
842 | the linked list in the first place. |
843 | .Sp |
844 | Note that if you have to look for strings that you don't know till runtime, |
845 | you can build an entire loop as a string and eval that to avoid recompiling |
846 | all your patterns all the time. |
847 | Together with setting $/ to input entire files as one record, this can |
848 | be very fast, often faster than specialized programs like fgrep. |
849 | The following scans a list of files (@files) |
850 | for a list of words (@words), and prints out the names of those files that |
851 | contain a match: |
852 | .nf |
853 | |
854 | .ne 12 |
855 | $search = \'while (<>) { study;\'; |
856 | foreach $word (@words) { |
857 | $search .= "++\e$seen{\e$ARGV} if /\eb$word\eb/;\en"; |
858 | } |
859 | $search .= "}"; |
860 | @ARGV = @files; |
861 | $/ = "\e177"; # something that doesn't occur |
862 | eval $search; # this screams |
863 | $/ = "\en"; # put back to normal input delim |
864 | foreach $file (sort keys(%seen)) { |
865 | print $file, "\en"; |
866 | } |
867 | |
868 | .fi |
869 | .Ip "substr(EXPR,OFFSET,LEN)" 8 2 |
870 | Extracts a substring out of EXPR and returns it. |
871 | First character is at offset 0, or whatever you've set $[ to. |
872 | If OFFSET is negative, starts that far from the end of the string. |
873 | You can use the substr() function as an lvalue, in which case EXPR must |
874 | be an lvalue. |
875 | If you assign something shorter than LEN, the string will shrink, and |
ae986130 |
876 | if you assign something longer than LEN, the string will grow to accommodate it. |
a687059c |
877 | To keep the string the same length you may need to pad or chop your value using |
878 | sprintf(). |
879 | .Ip "syscall(LIST)" 8 6 |
880 | .Ip "syscall LIST" 8 |
881 | Calls the system call specified as the first element of the list, passing |
882 | the remaining elements as arguments to the system call. |
883 | If unimplemented, produces a fatal error. |
884 | The arguments are interpreted as follows: if a given argument is numeric, |
885 | the argument is passed as an int. |
886 | If not, the pointer to the string value is passed. |
887 | You are responsible to make sure a string is pre-extended long enough |
888 | to receive any result that might be written into a string. |
889 | If your integer arguments are not literals and have never been interpreted |
890 | in a numeric context, you may need to add 0 to them to force them to look |
891 | like numbers. |
892 | .nf |
893 | |
894 | do 'syscall.h'; # may need to run makelib |
895 | syscall(&SYS_write, fileno(STDOUT), "hi there\en", 9); |
896 | |
897 | .fi |
898 | .Ip "system(LIST)" 8 6 |
899 | .Ip "system LIST" 8 |
900 | Does exactly the same thing as \*(L"exec LIST\*(R" except that a fork |
901 | is done first, and the parent process waits for the child process to complete. |
902 | Note that argument processing varies depending on the number of arguments. |
903 | The return value is the exit status of the program as returned by the wait() |
904 | call. |
905 | To get the actual exit value divide by 256. |
906 | See also |
907 | .IR exec . |
908 | .Ip "symlink(OLDFILE,NEWFILE)" 8 2 |
909 | Creates a new filename symbolically linked to the old filename. |
910 | Returns 1 for success, 0 otherwise. |
911 | On systems that don't support symbolic links, produces a fatal error at |
912 | run time. |
913 | To check for that, use eval: |
914 | .nf |
915 | |
916 | $symlink_exists = (eval \'symlink("","");\', $@ eq \'\'); |
917 | |
918 | .fi |
919 | .Ip "tell(FILEHANDLE)" 8 6 |
920 | .Ip "tell FILEHANDLE" 8 6 |
921 | .Ip "tell" 8 |
922 | Returns the current file position for FILEHANDLE. |
923 | FILEHANDLE may be an expression whose value gives the name of the actual |
924 | filehandle. |
925 | If FILEHANDLE is omitted, assumes the file last read. |
926 | .Ip "telldir(DIRHANDLE)" 8 5 |
927 | .Ip "telldir DIRHANDLE" 8 |
928 | Returns the current position of the readdir() routines on DIRHANDLE. |
929 | Value may be given to seekdir() to access a particular location in |
930 | a directory. |
931 | Has the same caveats about possible directory compaction as the corresponding |
932 | system library routine. |
933 | .Ip "time" 8 4 |
934 | Returns the number of non-leap seconds since January 1, 1970, UTC. |
935 | Suitable for feeding to gmtime() and localtime(). |
936 | .Ip "times" 8 4 |
937 | Returns a four-element array giving the user and system times, in seconds, for this |
938 | process and the children of this process. |
939 | .Sp |
940 | ($user,$system,$cuser,$csystem) = times; |
941 | .Sp |
942 | .Ip "tr/SEARCHLIST/REPLACEMENTLIST/" 8 5 |
943 | .Ip "y/SEARCHLIST/REPLACEMENTLIST/" 8 |
944 | Translates all occurrences of the characters found in the search list with |
945 | the corresponding character in the replacement list. |
946 | It returns the number of characters replaced. |
947 | If no string is specified via the =~ or !~ operator, |
948 | the $_ string is translated. |
949 | (The string specified with =~ must be a scalar variable, an array element, |
950 | or an assignment to one of those, i.e. an lvalue.) |
951 | For |
952 | .I sed |
953 | devotees, |
954 | .I y |
955 | is provided as a synonym for |
956 | .IR tr . |
957 | Examples: |
958 | .nf |
959 | |
960 | $ARGV[1] \|=~ \|y/A\-Z/a\-z/; \h'|3i'# canonicalize to lower case |
961 | |
962 | $cnt = tr/*/*/; \h'|3i'# count the stars in $_ |
963 | |
964 | ($HOST = $host) =~ tr/a\-z/A\-Z/; |
965 | |
966 | y/\e001\-@[\-_{\-\e177/ /; \h'|3i'# change non-alphas to space |
967 | |
968 | .fi |
969 | .Ip "umask(EXPR)" 8 4 |
970 | .Ip "umask EXPR" 8 |
ae986130 |
971 | .Ip "umask" 8 |
a687059c |
972 | Sets the umask for the process and returns the old one. |
973 | If EXPR is omitted, merely returns current umask. |
974 | .Ip "undef(EXPR)" 8 6 |
975 | .Ip "undef EXPR" 8 |
976 | .Ip "undef" 8 |
977 | Undefines the value of EXPR, which must be an lvalue. |
978 | Use only on a scalar value, an entire array, or a subroutine name (using &). |
979 | (Undef will probably not do what you expect on most predefined variables or |
980 | dbm array values.) |
981 | Always returns the undefined value. |
982 | You can omit the EXPR, in which case nothing is undefined, but you still |
983 | get an undefined value that you could, for instance, return from a subroutine. |
984 | Examples: |
985 | .nf |
986 | |
987 | .ne 6 |
988 | undef $foo; |
989 | undef $bar{'blurfl'}; |
990 | undef @ary; |
991 | undef %assoc; |
992 | undef &mysub; |
993 | return (wantarray ? () : undef) if $they_blew_it; |
994 | |
995 | .fi |
996 | .Ip "unlink(LIST)" 8 4 |
997 | .Ip "unlink LIST" 8 |
998 | Deletes a list of files. |
999 | Returns the number of files successfully deleted. |
1000 | .nf |
1001 | |
1002 | .ne 2 |
1003 | $cnt = unlink \'a\', \'b\', \'c\'; |
1004 | unlink @goners; |
1005 | unlink <*.bak>; |
1006 | |
1007 | .fi |
1008 | Note: unlink will not delete directories unless you are superuser and the |
1009 | .B \-U |
1010 | flag is supplied to |
1011 | .IR perl . |
1012 | Even if these conditions are met, be warned that unlinking a directory |
1013 | can inflict damage on your filesystem. |
1014 | Use rmdir instead. |
1015 | .Ip "unpack(TEMPLATE,EXPR)" 8 4 |
1016 | Unpack does the reverse of pack: it takes a string representing |
1017 | a structure and expands it out into an array value, returning the array |
1018 | value. |
1019 | The TEMPLATE has the same format as in the pack function. |
1020 | Here's a subroutine that does substring: |
1021 | .nf |
1022 | |
1023 | .ne 4 |
1024 | sub substr { |
1025 | local($what,$where,$howmuch) = @_; |
1026 | unpack("x$where a$howmuch", $what); |
1027 | } |
1028 | |
1029 | .ne 3 |
1030 | and then there's |
1031 | |
1032 | sub ord { unpack("c",$_[0]); } |
1033 | |
1034 | .fi |
1035 | .Ip "unshift(ARRAY,LIST)" 8 4 |
1036 | Does the opposite of a |
1037 | .IR shift . |
1038 | Or the opposite of a |
1039 | .IR push , |
1040 | depending on how you look at it. |
1041 | Prepends list to the front of the array, and returns the number of elements |
1042 | in the new array. |
1043 | .nf |
1044 | |
1045 | unshift(ARGV, \'\-e\') unless $ARGV[0] =~ /^\-/; |
1046 | |
1047 | .fi |
1048 | .Ip "utime(LIST)" 8 2 |
1049 | .Ip "utime LIST" 8 2 |
1050 | Changes the access and modification times on each file of a list of files. |
1051 | The first two elements of the list must be the NUMERICAL access and |
1052 | modification times, in that order. |
1053 | Returns the number of files successfully changed. |
1054 | The inode modification time of each file is set to the current time. |
1055 | Example of a \*(L"touch\*(R" command: |
1056 | .nf |
1057 | |
1058 | .ne 3 |
1059 | #!/usr/bin/perl |
1060 | $now = time; |
1061 | utime $now, $now, @ARGV; |
1062 | |
1063 | .fi |
1064 | .Ip "values(ASSOC_ARRAY)" 8 6 |
1065 | .Ip "values ASSOC_ARRAY" 8 |
1066 | Returns a normal array consisting of all the values of the named associative |
1067 | array. |
1068 | The values are returned in an apparently random order, but it is the same order |
1069 | as either the keys() or each() function would produce on the same array. |
1070 | See also keys() and each(). |
1071 | .Ip "vec(EXPR,OFFSET,BITS)" 8 2 |
1072 | Treats a string as a vector of unsigned integers, and returns the value |
1073 | of the bitfield specified. |
1074 | May also be assigned to. |
1075 | BITS must be a power of two from 1 to 32. |
1076 | .Sp |
1077 | Vectors created with vec() can also be manipulated with the logical operators |
1078 | |, & and ^, |
1079 | which will assume a bit vector operation is desired when both operands are |
1080 | strings. |
1081 | This interpretation is not enabled unless there is at least one vec() in |
1082 | your program, to protect older programs. |
1083 | .Ip "wait" 8 6 |
1084 | Waits for a child process to terminate and returns the pid of the deceased |
ae986130 |
1085 | process, or -1 if there are no child processes. |
a687059c |
1086 | The status is returned in $?. |
ae986130 |
1087 | If you expected a child and didn't find it, you probably had a call to |
1088 | system, a close on a pipe, or backticks between the fork and the wait. |
1089 | These constructs also do a wait and may have harvested your child process. |
a687059c |
1090 | .Ip "wantarray" 8 4 |
1091 | Returns true if the context of the currently executing subroutine |
1092 | is looking for an array value. |
1093 | Returns false if the context is looking for a scalar. |
1094 | .nf |
1095 | |
1096 | return wantarray ? () : undef; |
1097 | |
1098 | .fi |
1099 | .Ip "warn(LIST)" 8 4 |
1100 | .Ip "warn LIST" 8 |
1101 | Produces a message on STDERR just like \*(L"die\*(R", but doesn't exit. |
1102 | .Ip "write(FILEHANDLE)" 8 6 |
1103 | .Ip "write(EXPR)" 8 |
ae986130 |
1104 | .Ip "write" 8 |
a687059c |
1105 | Writes a formatted record (possibly multi-line) to the specified file, |
1106 | using the format associated with that file. |
1107 | By default the format for a file is the one having the same name is the |
1108 | filehandle, but the format for the current output channel (see |
1109 | .IR select ) |
1110 | may be set explicitly |
1111 | by assigning the name of the format to the $~ variable. |
1112 | .Sp |
1113 | Top of form processing is handled automatically: |
1114 | if there is insufficient room on the current page for the formatted |
1115 | record, the page is advanced, a special top-of-page format is used |
1116 | to format the new page header, and then the record is written. |
1117 | By default the top-of-page format is \*(L"top\*(R", but it |
1118 | may be set to the |
1119 | format of your choice by assigning the name to the $^ variable. |
1120 | .Sp |
1121 | If FILEHANDLE is unspecified, output goes to the current default output channel, |
1122 | which starts out as |
1123 | .I STDOUT |
1124 | but may be changed by the |
1125 | .I select |
1126 | operator. |
1127 | If the FILEHANDLE is an EXPR, then the expression is evaluated and the |
1128 | resulting string is used to look up the name of the FILEHANDLE at run time. |
1129 | For more on formats, see the section on formats later on. |
1130 | .Sp |
1131 | Note that write is NOT the opposite of read. |