[ NAME ]	[ SIZE ]	[ PERM ]	[ DATE ]	[ ACT ]
+FILE +DIR
a2p.pod	5.962 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl.pod	15.429 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5004delta.pod	54.921 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5005delta.pod	33.48 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5100delta.pod	53.413 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5101delta.pod	42.858 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5120delta.pod	87.193 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5121delta.pod	9.905 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5122delta.pod	9.378 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5123delta.pod	4.004 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5124delta.pod	3.586 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5140delta.pod	140.941 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5141delta.pod	7.779 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5142delta.pod	6.73 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5143delta.pod	7.578 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5160delta.pod	130.52 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5161delta.pod	5.998 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5162delta.pod	3.51 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl5163delta.pod	3.985 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl561delta.pod	121.786 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl56delta.pod	104.685 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl581delta.pod	37.168 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl582delta.pod	4.365 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl583delta.pod	6.187 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl584delta.pod	7.19 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl585delta.pod	5.751 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl586delta.pod	4.542 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl587delta.pod	8.161 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl588delta.pod	24.68 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl589delta.pod	52.637 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perl58delta.pod	112.215 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlaix.pod	18.768 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlamiga.pod	6.869 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlapi.pod	315.465 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlapio.pod	18.878 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlartistic.pod	6.846 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlbeos.pod	2.867 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlbook.pod	7.192 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlboot.pod	0.179 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlbot.pod	0.178 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlbs2000.pod	7.733 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlcall.pod	54.026 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlce.pod	8.723 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlcheat.pod	4.395 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlclib.pod	7.504 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlcn.pod	4.815 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlcommunity.pod	6.293 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlcygwin.pod	27.17 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldata.pod	36.331 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldbmfilter.pod	4.863 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldebguts.pod	36.789 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldebtut.pod	20.786 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldebug.pod	38.151 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldelta.pod	3.985 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldgux.pod	2.754 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldiag.pod	207.818 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldos.pod	10.275 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldsc.pod	24.837 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perldtrace.pod	6.209 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlebcdic.pod	67.605 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlembed.pod	35.209 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlepoc.pod	3.572 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlexperiment.pod	4.843 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq.pod	22.007 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq1.pod	13.519 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq2.pod	9.278 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq3.pod	37.464 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq4.pod	87.393 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq5.pod	54.113 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq6.pod	38.664 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq7.pod	36.352 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq8.pod	48.279 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfaq9.pod	14.709 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfork.pod	12.782 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlform.pod	16.287 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfreebsd.pod	1.554 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlfunc.pod	338.432 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlgit.pod	29.755 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlglossary.pod	110.655 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlgpl.pod	13.537 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlguts.pod	111.664 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhack.pod	35.03 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhacktips.pod	45.498 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhacktut.pod	6.068 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhaiku.pod	1.469 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhist.pod	43.319 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhpux.pod	28.065 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlhurd.pod	1.94 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlintern.pod	42.532 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlinterp.pod	30.002 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlintro.pod	22.085 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perliol.pod	33.027 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlipc.pod	70.165 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlirix.pod	4.291 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perljp.pod	7.572 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlko.pod	7.521 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perllexwarn.pod	14.612 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perllinux.pod	1.453 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perllocale.pod	51.435 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perllol.pod	10.935 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmacos.pod	0.978 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmacosx.pod	10.399 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmod.pod	24.041 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmodinstall.pod	12.412 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmodlib.pod	78.491 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmodstyle.pod	20.757 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmpeix.pod	14.236 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlmroapi.pod	3.128 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlnetware.pod	6.348 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlnewmod.pod	10.952 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlnumber.pod	8.156 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlobj.pod	33.653 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlootut.pod	25.604 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlop.pod	121.731 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlopenbsd.pod	1.176 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlopentut.pod	37.533 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlos2.pod	90.533 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlos390.pod	15.2 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlos400.pod	4.513 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlpacktut.pod	49.834 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlperf.pod	50.048 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlplan9.pod	5.005 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlpod.pod	21.27 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlpodspec.pod	66.203 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlpolicy.pod	19.726 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlport.pod	82.635 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlpragma.pod	5.105 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlqnx.pod	4.145 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlre.pod	100.761 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlreapi.pod	25.168 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlrebackslash.pod	25.644 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlrecharclass.pod	34.188 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlref.pod	28.319 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlreftut.pod	18.232 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlreguts.pod	35.995 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlrequick.pod	17.499 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlreref.pod	14.19 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlretut.pod	115.128 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlriscos.pod	1.493 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlrun.pod	49.575 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsec.pod	22.768 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsolaris.pod	28.63 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsource.pod	6.194 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlstyle.pod	8.416 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsub.pod	55.153 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsymbian.pod	15.439 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlsyn.pod	41.044 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlthrtut.pod	45.407 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltie.pod	37.02 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltoc.pod	638.995 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltodo.pod	0.354 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltooc.pod	0.179 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltoot.pod	0.179 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltrap.pod	40.281 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltru64.pod	7.552 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perltw.pod	5.151 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlunicode.pod	70.891 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlunifaq.pod	13.314 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perluniintro.pod	35.443 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perluniprops.pod	229.736 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlunitut.pod	7.756 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlutil.pod	9.679 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perluts.pod	3.105 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlvar.pod	69.188 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlvmesa.pod	3.881 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlvms.pod	51.333 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlvos.pod	5.823 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlwin32.pod	34.581 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlxs.pod	71.663 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlxstut.pod	48.517 KB	-rw-r--r--	2023-10-25 12:41	R E G D
perlxstypemap.pod	22.966 KB	-rw-r--r--	2023-10-25 12:41	R E G D
REQUEST EXIT

, in its own lexical scope. However, if the script dies, C<$@> will not be set. The value of C<$Config{sitelib}> is also determined in C code and not read from C, which is not loaded. The code is executed I early. For example, any changes made to C<@INC> will show up in the output of `perl -V`. Of course, C blocks will be likewise executed very late. To determine at runtime if this capability has been compiled in your perl, you can check the value of C<$Config{usesitecustomize}>. =item B<-F>I X<-F> specifies the pattern to split on if B<-a> is also in effect. The pattern may be surrounded by C, C<"">, or C<''>, otherwise it will be put in single quotes. You can't use literal whitespace in the pattern. =item B<-h> X<-h> prints a summary of the options. =item B<-i>[I] X<-i> X specifies that files processed by the CE> construct are to be edited in-place. It does this by renaming the input file, opening the output file by the original name, and selecting that output file as the default for print() statements. The extension, if supplied, is used to modify the name of the old file to make a backup copy, following these rules: If no extension is supplied, no backup is made and the current file is overwritten. If the extension doesn't contain a C<*>, then it is appended to the end of the current filename as a suffix. If the extension does contain one or more C<*> characters, then each C<*> is replaced with the current filename. In Perl terms, you could think of this as: ($backup = $extension) =~ s/\*/$file_name/g; This allows you to add a prefix to the backup file, instead of (or in addition to) a suffix: $ perl -pi'orig_*' -e 's/bar/baz/' fileA # backup to # 'orig_fileA' Or even to place backup copies of the original files into another directory (provided the directory already exists): $ perl -pi'old/*.orig' -e 's/bar/baz/' fileA # backup to # 'old/fileA.orig' These sets of one-liners are equivalent: $ perl -pi -e 's/bar/baz/' fileA # overwrite current file $ perl -pi'*' -e 's/bar/baz/' fileA # overwrite current file $ perl -pi'.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig' $ perl -pi'*.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig' From the shell, saying $ perl -p -i.orig -e "s/foo/bar/; ... " is the same as using the program: #!/usr/bin/perl -pi.orig s/foo/bar/; which is equivalent to #!/usr/bin/perl $extension = '.orig'; LINE: while (<>) { if ($ARGV ne $oldargv) { if ($extension !~ /\*/) { $backup = $ARGV . $extension; } else { ($backup = $extension) =~ s/\*/$ARGV/g; } rename($ARGV, $backup); open(ARGVOUT, ">$ARGV"); select(ARGVOUT); $oldargv = $ARGV; } s/foo/bar/; } continue { print; # this prints to original filename } select(STDOUT); except that the B<-i> form doesn't need to compare $ARGV to $oldargv to know when the filename has changed. It does, however, use ARGVOUT for the selected filehandle. Note that STDOUT is restored as the default output filehandle after the loop. As shown above, Perl creates the backup file whether or not any output is actually changed. So this is just a fancy way to copy files: $ perl -p -i'/some/file/path/*' -e 1 file1 file2 file3... or $ perl -p -i'.orig' -e 1 file1 file2 file3... You can use C without parentheses to locate the end of each input file, in case you want to append to each file, or reset line numbering (see example in L). If, for a given file, Perl is unable to create the backup file as specified in the extension then it will skip that file and continue on with the next one (if it exists). For a discussion of issues surrounding file permissions and B<-i>, see L. You cannot use B<-i> to create directories or to strip extensions from files. Perl does not expand C<~> in filenames, which is good, since some folks use it for their backup files: $ perl -pi~ -e 's/foo/bar/' file1 file2 file3... Note that because B<-i> renames or deletes the original file before creating a new file of the same name, Unix-style soft and hard links will not be preserved. Finally, the B<-i> switch does not impede execution when no files are given on the command line. In this case, no backup is made (the original file cannot, of course, be determined) and processing proceeds from STDIN to STDOUT as might be expected. =item B<-I>I X<-I> X<@INC> Directories specified by B<-I> are prepended to the search path for modules (C<@INC>). =item B<-l>[I] X<-l> X<$/> X<$\> enables automatic line-ending processing. It has two separate effects. First, it automatically chomps C<$/> (the input record separator) when used with B<-n> or B<-p>. Second, it assigns C<$\> (the output record separator) to have the value of I so that any print statements will have that separator added back on. If I is omitted, sets C<$\> to the current value of C<$/>. For instance, to trim lines to 80 columns: perl -lpe 'substr($_, 80) = ""' Note that the assignment C<$\ = $/> is done when the switch is processed, so the input record separator can be different than the output record separator if the B<-l> switch is followed by a B<-0> switch: gnufind / -print0 | perl -ln0e 'print "found $_" if -p' This sets C<$\> to newline and then sets C<$/> to the null character. =item B<-m>[B<->]I X<-m> X<-M> =item B<-M>[B<->]I =item B<-M>[B<->]I<'module ...'> =item B<-[mM]>[B<->]I B<-m>I executes C I C<();> before executing your program. B<-M>I executes C I C<;> before executing your program. You can use quotes to add extra code after the module name, e.g., C<'-MI qw(foo bar)'>. If the first character after the B<-M> or B<-m> is a dash (B<->) then the 'use' is replaced with 'no'. A little builtin syntactic sugar means you can also say B<-mI=foo,bar> or B<-MI=foo,bar> as a shortcut for B<'-MI qw(foo bar)'>. This avoids the need to use quotes when importing symbols. The actual code generated by B<-MI=foo,bar> is C. Note that the C<=> form removes the distinction between B<-m> and B<-M>. A consequence of this is that B<-MI=number> never does a version check, unless C::import()> itself is set up to do a version check, which could happen for example if I inherits from L. =item B<-n> X<-n> causes Perl to assume the following loop around your program, which makes it iterate over filename arguments somewhat like I or I: LINE: while (<>) { ... # your program goes here } Note that the lines are not printed by default. See L to have lines printed. If a file named by an argument cannot be opened for some reason, Perl warns you about it and moves on to the next file. Also note that C<< <> >> passes command line arguments to L, which doesn't necessarily interpret them as file names. See L for possible security implications. Here is an efficient way to delete all files that haven't been modified for at least a week: find . -mtime +7 -print | perl -nle unlink This is faster than using the B<-exec> switch of I because you don't have to start a process on every filename found. It does suffer from the bug of mishandling newlines in pathnames, which you can fix if you follow the example under B<-0>. C and C blocks may be used to capture control before or after the implicit program loop, just as in I. =item B<-p> X<-p> causes Perl to assume the following loop around your program, which makes it iterate over filename arguments somewhat like I: LINE: while (<>) { ... # your program goes here } continue { print or die "-p destination: $!\n"; } If a file named by an argument cannot be opened for some reason, Perl warns you about it, and moves on to the next file. Note that the lines are printed automatically. An error occurring during printing is treated as fatal. To suppress printing use the B<-n> switch. A B<-p> overrides a B<-n> switch. C and C blocks may be used to capture control before or after the implicit loop, just as in I. =item B<-s> X<-s> enables rudimentary switch parsing for switches on the command line after the program name but before any filename arguments (or before an argument of B<-->). Any switch found there is removed from @ARGV and sets the corresponding variable in the Perl program. The following program prints "1" if the program is invoked with a B<-xyz> switch, and "abc" if it is invoked with B<-xyz=abc>. #!/usr/bin/perl -s if ($xyz) { print "$xyz\n" } Do note that a switch like B<--help> creates the variable C<${-help}>, which is not compliant with C. Also, when using this option on a script with warnings enabled you may get a lot of spurious "used only once" warnings. =item B<-S> X<-S> makes Perl use the PATH environment variable to search for the program unless the name of the program contains path separators. On some platforms, this also makes Perl append suffixes to the filename while searching for it. For example, on Win32 platforms, the ".bat" and ".cmd" suffixes are appended if a lookup for the original name fails, and if the name does not already end in one of those suffixes. If your Perl was compiled with C turned on, using the B<-Dp> switch to Perl shows how the search progresses. Typically this is used to emulate C<#!> startup on platforms that don't support C<#!>. It's also convenient when debugging a script that uses C<#!>, and is thus normally found by the shell's $PATH search mechanism. This example works on many platforms that have a shell compatible with Bourne shell: #!/usr/bin/perl eval 'exec /usr/bin/perl -wS $0 ${1+"$@"}' if $running_under_some_shell; The system ignores the first line and feeds the program to F, which proceeds to try to execute the Perl program as a shell script. The shell executes the second line as a normal shell command, and thus starts up the Perl interpreter. On some systems $0 doesn't always contain the full pathname, so the B<-S> tells Perl to search for the program if necessary. After Perl locates the program, it parses the lines and ignores them because the variable $running_under_some_shell is never true. If the program will be interpreted by csh, you will need to replace C<${1+"$@"}> with C<$*>, even though that doesn't understand embedded spaces (and such) in the argument list. To start up I rather than I, some systems may have to replace the C<#!> line with a line containing just a colon, which will be politely ignored by Perl. Other systems can't control that, and need a totally devious construct that will work under any of I, I, or Perl, such as the following: eval '(exit $?0)' && eval 'exec perl -wS $0 ${1+"$@"}' & eval 'exec /usr/bin/perl -wS $0 $argv:q' if $running_under_some_shell; If the filename supplied contains directory separators (and so is an absolute or relative pathname), and if that file is not found, platforms that append file extensions will do so and try to look for the file with those extensions added, one by one. On DOS-like platforms, if the program does not contain directory separators, it will first be searched for in the current directory before being searched for on the PATH. On Unix platforms, the program will be searched for strictly on the PATH. =item B<-t> X<-t> Like B<-T>, but taint checks will issue warnings rather than fatal errors. These warnings can now be controlled normally with C. B!> This is meant to be used I as a temporary development aid while securing legacy code: for real production code and for new secure code written from scratch, always use the real B<-T>. =item B<-T> X<-T> turns on "taint" so you can test them. Ordinarily these checks are done only when running setuid or setgid. It's a good idea to turn them on explicitly for programs that run on behalf of someone else whom you might not necessarily trust, such as CGI programs or any internet servers you might write in Perl. See L for details. For security reasons, this option must be seen by Perl quite early; usually this means it must appear early on the command line or in the C<#!> line for systems which support that construct. =item B<-u> X<-u> This switch causes Perl to dump core after compiling your program. You can then in theory take this core dump and turn it into an executable file by using the I program (not supplied). This speeds startup at the expense of some disk space (which you can minimize by stripping the executable). (Still, a "hello world" executable comes out to about 200K on my machine.) If you want to execute a portion of your program before dumping, use the dump() operator instead. Note: availability of I is platform specific and may not be available for a specific port of Perl. =item B<-U> X<-U> allows Perl to do unsafe operations. Currently the only "unsafe" operations are attempting to unlink directories while running as superuser and running setuid programs with fatal taint checks turned into warnings. Note that warnings must be enabled along with this option to actually I the taint-check warnings. =item B<-v> X<-v> prints the version and patchlevel of your perl executable. =item B<-V> X<-V> prints summary of the major perl configuration values and the current values of @INC. =item B<-V:>I Prints to STDOUT the value of the named configuration variable(s), with multiples when your C> argument looks like a regex (has non-letters). For example: $ perl -V:libc libc='/lib/libc-2.2.4.so'; $ perl -V:lib. libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc'; libc='/lib/libc-2.2.4.so'; $ perl -V:lib.* libpth='/usr/local/lib /lib /usr/lib'; libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc'; lib_ext='.a'; libc='/lib/libc-2.2.4.so'; libperl='libperl.a'; .... Additionally, extra colons can be used to control formatting. A trailing colon suppresses the linefeed and terminator ";", allowing you to embed queries into shell commands. (mnemonic: PATH separator ":".) $ echo "compression-vars: " `perl -V:z.*: ` " are here !" compression-vars: zcat='' zip='zip' are here ! A leading colon removes the "name=" part of the response, this allows you to map to the name you need. (mnemonic: empty label) $ echo "goodvfork="`./perl -Ilib -V::usevfork` goodvfork=false; Leading and trailing colons can be used together if you need positional parameter values without the names. Note that in the case below, the C params are returned in alphabetical order. $ echo building_on `perl -V::osname: -V::PERL_API_.*:` now building_on 'linux' '5' '1' '9' now =item B<-w> X<-w> prints warnings about dubious constructs, such as variable names mentioned only once and scalar variables used before being set; redefined subroutines; references to undefined filehandles; filehandles opened read-only that you are attempting to write on; values used as a number that don't I like numbers; using an array as though it were a scalar; if your subroutines recurse more than 100 deep; and innumerable other things. This switch really just enables the global C<$^W> variable; normally, the lexically scoped C pragma is preferred. You can disable or promote into fatal errors specific warnings using C<__WARN__> hooks, as described in L and L. See also L and L. A fine-grained warning facility is also available if you want to manipulate entire classes of warnings; see L or L. =item B<-W> X<-W> Enables all warnings regardless of C or C<$^W>. See L. =item B<-X> X<-X> Disables all warnings regardless of C or C<$^W>. See L. =item B<-x> X<-x> =item B<-x>I tells Perl that the program is embedded in a larger chunk of unrelated text, such as in a mail message. Leading garbage will be discarded until the first line that starts with C<#!> and contains the string "perl". Any meaningful switches on that line will be applied. All references to line numbers by the program (warnings, errors, ...) will treat the C<#!> line as the first line. Thus a warning on the 2nd line of the program, which is on the 100th line in the file will be reported as line 2, not as line 100. This can be overridden by using the C<#line> directive. (See L) If a directory name is specified, Perl will switch to that directory before running the program. The B<-x> switch controls only the disposal of leading garbage. The program must be terminated with C<__END__> if there is trailing garbage to be ignored; the program can process any or all of the trailing garbage via the C filehandle if desired. The directory, if specified, must appear immediately following the B<-x> with no intervening whitespace. =back =head1 ENVIRONMENT X =over 12 =item HOME X Used if C has no argument. =item LOGDIR X Used if C has no argument and HOME is not set. =item PATH X Used in executing subprocesses, and in finding the program if B<-S> is used. =item PERL5LIB X A list of directories in which to look for Perl library files before looking in the standard library and the current directory. Any architecture-specific directories under the specified locations are automatically included if they exist, with this lookup done at interpreter startup time. If PERL5LIB is not defined, PERLLIB is used. Directories are separated (like in PATH) by a colon on Unixish platforms and by a semicolon on Windows (the proper path separator being given by the command C>). When running taint checks, either because the program was running setuid or setgid, or the B<-T> or B<-t> switch was specified, neither PERL5LIB nor PERLLIB is consulted. The program should instead say: use lib "/my/directory"; =item PERL5OPT X Command-line options (switches). Switches in this variable are treated as if they were on every Perl command line. Only the B<-[CDIMUdmtwW]> switches are allowed. When running taint checks (either because the program was running setuid or setgid, or because the B<-T> or B<-t> switch was used), this variable is ignored. If PERL5OPT begins with B<- T>, tainting will be enabled and subsequent options ignored. If PERL5OPT begins with B<-t>, tainting will be enabled, a writable dot removed from @INC, and subsequent options honored. =item PERLIO X A space (or colon) separated list of PerlIO layers. If perl is built to use PerlIO system for IO (the default) these layers affect Perl's IO. It is conventional to start layer names with a colon (for example, C<:perlio>) to emphasize their similarity to variable "attributes". But the code that parses layer specification strings, which is also used to decode the PERLIO environment variable, treats the colon as a separator. An unset or empty PERLIO is equivalent to the default set of layers for your platform; for example, C<:unix:perlio> on Unix-like systems and C<:unix:crlf> on Windows and other DOS-like systems. The list becomes the default for I Perl's IO. Consequently only built-in layers can appear in this list, as external layers (such as C<:encoding()>) need IO in order to load them!. See L<"open pragma"|open> for how to add external encodings as defaults. Layers it makes sense to include in the PERLIO environment variable are briefly summarized below. For more details see L. =over 8 =item :bytes X<:bytes> A pseudolayer that turns the C<:utf8> flag I for the layer below; unlikely to be useful on its own in the global PERLIO environment variable. You perhaps were thinking of C<:crlf:bytes> or C<:perlio:bytes>. =item :crlf X<:crlf> A layer which does CRLF to C<"\n"> translation distinguishing "text" and "binary" files in the manner of MS-DOS and similar operating systems. (It currently does I mimic MS-DOS as far as treating of Control-Z as being an end-of-file marker.) =item :mmap X<:mmap> A layer that implements "reading" of files by using I(2) to make an entire file appear in the process's address space, and then using that as PerlIO's "buffer". =item :perlio X<:perlio> This is a re-implementation of stdio-like buffering written as a PerlIO layer. As such it will call whatever layer is below it for its operations, typically C<:unix>. =item :pop X<:pop> An experimental pseudolayer that removes the topmost layer. Use with the same care as is reserved for nitroglycerine. =item :raw X<:raw> A pseudolayer that manipulates other layers. Applying the C<:raw> layer is equivalent to calling C. It makes the stream pass each byte as-is without translation. In particular, both CRLF translation and intuiting C<:utf8> from the locale are disabled. Unlike in earlier versions of Perl, C<:raw> is I just the inverse of C<:crlf>: other layers which would affect the binary nature of the stream are also removed or disabled. =item :stdio X<:stdio> This layer provides a PerlIO interface by wrapping system's ANSI C "stdio" library calls. The layer provides both buffering and IO. Note that the C<:stdio> layer does I do CRLF translation even if that is the platform's normal behaviour. You will need a C<:crlf> layer above it to do that. =item :unix X<:unix> Low-level layer that calls C, C, C, etc. =item :utf8 X<:utf8> A pseudolayer that enables a flag in the layer below to tell Perl that output should be in utf8 and that input should be regarded as already in valid utf8 form. B Generally C<:encoding(utf8)> is the best option when reading UTF-8 encoded data. =item :win32 X<:win32> On Win32 platforms this I layer uses native "handle" IO rather than a Unix-like numeric file descriptor layer. Known to be buggy in this release (5.14). =back The default set of layers should give acceptable results on all platforms For Unix platforms that will be the equivalent of "unix perlio" or "stdio". Configure is set up to prefer the "stdio" implementation if the system's library provides for fast access to the buffer; otherwise, it uses the "unix perlio" implementation. On Win32 the default in this release (5.14) is "unix crlf". Win32's "stdio" has a number of bugs/mis-features for Perl IO which are somewhat depending on the version and vendor of the C compiler. Using our own C layer as the buffer avoids those issues and makes things more uniform. The C layer provides CRLF conversion as well as buffering. This release (5.14) uses C as the bottom layer on Win32, and so still uses the C compiler's numeric file descriptor routines. There is an experimental native C layer, which is expected to be enhanced and should eventually become the default under Win32. The PERLIO environment variable is completely ignored when Perl is run in taint mode. =item PERLIO_DEBUG X If set to the name of a file or device, certain operations of PerlIO subsystem will be logged to that file, which is opened in append mode Typical uses are in Unix: % env PERLIO_DEBUG=/dev/tty perl script ... and under Win32, the approximately equivalent: > set PERLIO_DEBUG=CON perl script ... This functionality is disabled for setuid scripts and for scripts run with B<-T>. =item PERLLIB X A list of directories in which to look for Perl library files before looking in the standard library and the current directory. If PERL5LIB is defined, PERLLIB is not used. The PERLLIB environment variable is completely ignored when Perl is run in taint mode. =item PERL5DB X The command used to load the debugger code. The default is: BEGIN { require "perl5db.pl" } The PERL5DB environment variable is only used when Perl is started with a bare B<-d> switch. =item PERL5DB_THREADED X If set to a true value, indicates to the debugger that the code being debugged uses threads. =item PERL5SHELL (specific to the Win32 port) X On Win32 ports only, may be set to an alternative shell that Perl must use internally for executing "backtick" commands or system(). Default is C on WindowsNT and C on Windows95. The value is considered space-separated. Precede any character that needs to be protected, like a space or backslash, with another backslash. Note that Perl doesn't use COMSPEC for this purpose because COMSPEC has a high degree of variability among users, leading to portability concerns. Besides, Perl can use a shell that may not be fit for interactive use, and setting COMSPEC to such a shell may interfere with the proper functioning of other programs (which usually look in COMSPEC to find a shell fit for interactive use). Before Perl 5.10.0 and 5.8.8, PERL5SHELL was not taint checked when running external commands. It is recommended that you explicitly set (or delete) C<$ENV{PERL5SHELL}> when running in taint mode under Windows. =item PERL_ALLOW_NON_IFS_LSP (specific to the Win32 port) X Set to 1 to allow the use of non-IFS compatible LSPs (Layered Service Providers). Perl normally searches for an IFS-compatible LSP because this is required for its emulation of Windows sockets as real filehandles. However, this may cause problems if you have a firewall such as I, which requires that all applications use its LSP but which is not IFS-compatible, because clearly Perl will normally avoid using such an LSP. Setting this environment variable to 1 means that Perl will simply use the first suitable LSP enumerated in the catalog, which keeps I happy--and in that particular case Perl still works too because I's LSP actually plays other games which allow applications requiring IFS compatibility to work. =item PERL_DEBUG_MSTATS X Relevant only if Perl is compiled with the C included with the Perl distribution; that is, if C is "define". If set, this dumps out memory statistics after execution. If set to an integer greater than one, also dumps out memory statistics after compilation. =item PERL_DESTRUCT_LEVEL X Relevant only if your Perl executable was built with B<-DDEBUGGING>, this controls the behaviour of global destruction of objects and other references. See L for more information. =item PERL_DL_NONLAZY X Set to C<"1"> to have Perl resolve I undefined symbols when it loads a dynamic library. The default behaviour is to resolve symbols when they are used. Setting this variable is useful during testing of extensions, as it ensures that you get an error on misspelled function names even if the test suite doesn't call them. =item PERL_ENCODING X If using the C pragma without an explicit encoding name, the PERL_ENCODING environment variable is consulted for an encoding name. =item PERL_HASH_SEED X (Since Perl 5.8.1.) Used to randomize Perl's internal hash function. To emulate the pre-5.8.1 behaviour, set to an integer; C<"0"> means exactly the same order as in 5.8.0. "Pre-5.8.1" means, among other things, that hash keys will always have the same ordering between different runs of Perl. Most hashes by default return elements in the same order as in Perl 5.8.0. On a hash by hash basis, if pathological data is detected during a hash key insertion, then that hash will switch to an alternative random hash seed. The default behaviour is to randomize unless the PERL_HASH_SEED is set. If Perl has been compiled with B<-DUSE_HASH_SEED_EXPLICIT>, the default behaviour is I to randomize unless the PERL_HASH_SEED is set. If PERL_HASH_SEED is unset or set to a non-numeric string, Perl uses the pseudorandom seed supplied by the operating system and libraries. B. Hashes are randomized to protect against local and remote attacks against Perl code. By manually setting a seed, this protection may be partially or completely lost. See L and L for more information. =item PERL_HASH_SEED_DEBUG X (Since Perl 5.8.1.) Set to C<"1"> to display (to STDERR) the value of the hash seed at the beginning of execution. This, combined with L is intended to aid in debugging nondeterministic behaviour caused by hash randomization. B: by knowing it, one can craft a denial-of-service attack against Perl code, even remotely; see L for more information. B to people who don't need to know it. See also hash_seed() in L. =item PERL_MEM_LOG X If your Perl was configured with B<-Accflags=-DPERL_MEM_LOG>, setting the environment variable C enables logging debug messages. The value has the form C<< >[m][s][t] >>, where C> is the file descriptor number you want to write to (2 is default), and the combination of letters specifies that you want information about (m)emory and/or (s)v, optionally with (t)imestamps. For example, C logs all information to stdout. You can write to other opened file descriptors in a variety of ways: $ 3>foo3 PERL_MEM_LOG=3m perl ... =item PERL_ROOT (specific to the VMS port) X A translation-concealed rooted logical name that contains Perl and the logical device for the @INC path on VMS only. Other logical names that affect Perl on VMS include PERLSHR, PERL_ENV_TABLES, and SYS$TIMEZONE_DIFFERENTIAL, but are optional and discussed further in L and in F in the Perl source distribution. =item PERL_SIGNALS X Available in Perls 5.8.1 and later. If set to C<"unsafe">, the pre-Perl-5.8.0 signal behaviour (which is immediate but unsafe) is restored. If set to C, then safe (but deferred) signals are used. See L. =item PERL_UNICODE X Equivalent to the B<-C> command-line switch. Note that this is not a boolean variable. Setting this to C<"1"> is not the right way to "enable Unicode" (whatever that would mean). You can use C<"0"> to "disable Unicode", though (or alternatively unset PERL_UNICODE in your shell before starting Perl). See the description of the B<-C> switch for more information. =item SYS$LOGIN (specific to the VMS port) X Used if chdir has no argument and HOME and LOGDIR are not set. =back Perl also has environment variables that control how Perl handles data specific to particular natural languages; see L. Perl and its various modules and components, including its test frameworks, may sometimes make use of certain other environment variables. Some of these are specific to a particular platform. Please consult the appropriate module documentation and any documentation for your platform (like L, L, L, L, etc) for variables peculiar to those specific situations. Perl makes all environment variables available to the program being executed, and passes these along to any child processes it starts. However, programs running setuid would do well to execute the following lines before doing anything else, just to keep people honest: $ENV{PATH} = "/bin:/usr/bin"; # or whatever you need $ENV{SHELL} = "/bin/sh" if exists $ENV{SHELL}; delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};