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Diffstat (limited to 'pod/perlrun.pod')
| -rw-r--r-- | pod/perlrun.pod | 83 |
1 files changed, 53 insertions, 30 deletions
diff --git a/pod/perlrun.pod b/pod/perlrun.pod index de7116d939..1e3279e374 100644 --- a/pod/perlrun.pod +++ b/pod/perlrun.pod @@ -224,33 +224,33 @@ runs the script under the control of a debugging or tracing module installed as Devel::foo. E.g., B<-d:DProf> executes the script using the Devel::DProf profiler. See L<perldebug>. -=item B<-D>I<number> +=item B<-D>I<letters> -=item B<-D>I<list> +=item B<-D>I<number> sets debugging flags. To watch how it executes your script, use -B<-D14>. (This works only if debugging is compiled into your -Perl.) Another nice value is B<-D1024>, which lists your compiled -syntax tree. And B<-D512> displays compiled regular expressions. As an -alternative specify a list of letters instead of numbers (e.g., B<-D14> is +B<-Dtls>. (This works only if debugging is compiled into your +Perl.) Another nice value is B<-Dx>, which lists your compiled +syntax tree. And B<-Dr> displays compiled regular expressions. As an +alternative, specify a number instead of list of letters (e.g., B<-D14> is equivalent to B<-Dtls>): - 1 p Tokenizing and Parsing - 2 s Stack Snapshots - 4 l Label Stack Processing - 8 t Trace Execution - 16 o Operator Node Construction - 32 c String/Numeric Conversions - 64 P Print Preprocessor Command for -P - 128 m Memory Allocation - 256 f Format Processing - 512 r Regular Expression Parsing - 1024 x Syntax Tree Dump - 2048 u Tainting Checks - 4096 L Memory Leaks (not supported anymore) - 8192 H Hash Dump -- usurps values() - 16384 X Scratchpad Allocation - 32768 D Cleaning Up + 1 p Tokenizing and parsing + 2 s Stack snapshots + 4 l Context (loop) stack processing + 8 t Trace execution + 16 o Method and overloading resolution + 32 c String/numeric conversions + 64 P Print preprocessor command for -P + 128 m Memory allocation + 256 f Format processing + 512 r Regular expression parsing and execution + 1024 x Syntax tree dump + 2048 u Tainting checks + 4096 L Memory leaks (not supported anymore) + 8192 H Hash dump -- usurps values() + 16384 X Scratchpad allocation + 32768 D Cleaning up =item B<-e> I<commandline> @@ -376,8 +376,10 @@ B<awk>: } Note that the lines are not printed by default. See B<-p> to have -lines printed. Here is an efficient way to delete all files older than -a week: +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. + +Here is an efficient way to delete all files older than a week: find . -mtime +7 -print | perl -nle 'unlink;' @@ -396,11 +398,14 @@ makes it iterate over filename arguments somewhat like B<sed>: while (<>) { ... # your script goes here } continue { - print; + print or die "-p destination: $!\n"; } -Note that the lines are printed automatically. To suppress printing -use the B<-n> switch. A B<-p> overrides a B<-n> switch. +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 occuring during printing is +treated as fatal. To suppress printing use the B<-n> switch. A B<-p> +overrides a B<-n> switch. C<BEGIN> and C<END> blocks may be used to capture control before or after the implicit loop, just as in awk. @@ -426,9 +431,27 @@ prints "true" if and only if the script is invoked with a B<-xyz> switch. =item B<-S> makes Perl use the PATH environment variable to search for the -script (unless the name of the script starts with a slash). Typically -this is used to emulate #! startup on machines that don't support #!, -in the following manner: +script (unless the name of the script contains directory 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 DEBUGGING turned +on, using the -Dp switch to Perl shows how the search progresses. + +If the file supplied contains directory separators (i.e. it is an +absolute or relative pathname), and if the 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 script 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 +script will be searched for strictly on the PATH. + +Typically this is used to emulate #! startup on platforms that +don't support #!. This example works on many platforms that +have a shell compatible with Bourne shell: #!/usr/bin/perl eval 'exec /usr/bin/perl -S $0 ${1+"$@"}' |