perl_oneliners.txt

# --------------------------------------------------------------
# Perl one-liners
# --------------------------------------------------------------

# substitue one word with another in all files in a directory:
perl -pi -e 's/word/another/g' *

# dos-2-unix as a one-liner:
perl -pi -e 's/\r\n/\n/' myscript.cgi

# --------------------------------------------------------------
# stripping the font tags:
perl -0777 -pi -e 's/<\/?FONT[^>]*>//gi' filename

# --------------------------------------------------------------
# list CLASSPATH entries on separate lines (originally they are ":"-separated):
echo $CLASSPATH | perl -e '$_=<>;s/:/\n/g;print;'

# --------------------------------------------------------------
# make a nice listing of files (use ls, find, grep to lacate files):
ls *.java | perl -nle '$n=$_;$h="-"x60 . "\n";print "$h$n\n$h"; open(in,$n); map {chomp;print}<in>;' > ~/java.txt
ls *.xsl | perl -ne '$n=$_;$h="-"x60 . "\n";print "$h$n$h"; open(in,$n); map {print}<in>;' > ~/xsl.txt
ls *.java | perl -nle '$n=$_;$h="-"x60 . "\n";{local $/=undef;open(in,$n);$s=<in>;}print "$h$n\n$h$s\n";' > ~/java.txt
perl -e '$h="-"x60 . "\n";for $n (<*.java>){{local $/=undef;open(in,$n);$s=<in>;}print "$h$n\n$h$s\n";}' > ~/ttt.txt

# standalone:

#! /usr/local/bin/perl
map{open(IN,$_);print "-"x60 ."\n$_\n"."-"x60 ."\n";map{print}<IN>;close(IN);}glob("*.java");

#! /usr/local/bin/perl
$h="-"x60 . "\n";for $n (<*.java>){local $/=undef;open(IN,$n);$s=<IN>;print "$h$n\n$h$s\n";}

#! /usr/local/bin/perl
# getall.pl
# usage: ls -1 * | xargs getall.pl > out.txt
map{open(IN,$_);print "-"x60 ."\n$_\n"."-"x60 ."\n";map{print}<IN>;close(IN);} @ARGV;

# --------------------------------------------------------------
# rename many files simultaneously (here it renames *.tar into *.tar7):
ls -1 *.tar | perl -nle '$old=$_;s/(\.+)tar/$1tar7/;rename($old, $_);' -

# --------------------------------------------------------------
# print help for all commands of perforce (p4) source control system:
p4 help commands | perl -nle 'm/^\s+(\w+)\s/; print "$1\n";' - | xargs p4 help

# --------------------------------------------------------------
# sum first and last fields (using -a option to split input into @F):
perl -lane 'print $F[0] + $F[-1]' *

# --------------------------------------------------------------
# identify text files:
perl -le 'for(@ARGV) {print if -f && -T _}' *

# --------------------------------------------------------------
# remove (most) comments from C program:
perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c

# --------------------------------------------------------------
# make file a month younger than today, defeating reaper daemons:
perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' *

# --------------------------------------------------------------
# find first unused uid:
perl -le '$i++ while getpwuid($i); print $i'

# --------------------------------------------------------------
# display reasonable manpath (072 is code of ":"):
echo $PATH | perl -nl -072 -e 's![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}'

# --------------------------------------------------------------
# Print a message if a daylight savings time change occurs within the next 5 days:
print "\aTIME CHANGE COMING!\n" if (localtime(time))[8] ne (localtime(time+5*24*60*60))[8];
perl -e 'print "$_\n" for @INC'

# --------------------------------------------------------------