Difference between revisions of "Perl/Scripts"

Revision as of 01:24, 5 September 2007

The following is a compilation of useful one-line scripts for Perl. The original was compiled by Tom Christiansen, however, I have converted it into the wiki format and have added more examples (always adding more).

Perl one-liners

• run contents of "my_file" as a program

perl my_file

• run debugger "stand-alone"

perl -d -e 42

• run program, but with warnings

perl -w my_file

• run program under debugger

perl -d my_file

• just check syntax, with warnings

perl -wc my_file

• useful at end of "find foo -print"

perl -nle unlink

• simplest one-liner program

perl -e 'print "hello world!\n"'

• add first and penultimate columns

perl -lane 'print $F[0] + $F[-2]'

• just lines 15 to 17

perl -ne 'print if 15 .. 17' *.pod

• in-place edit of *.c files changing all foo to bar

perl -p -i.bak -e 's/\bfoo\b/bar/g' *.c

• command-line that prints the first 50 lines (cheaply)

perl -pe 'exit if $. > 50' f1 f2 f3 ...

• delete first 10 lines

perl -i.old -ne 'print unless 1 .. 10' foo.txt

• change all the isolated oldvar occurrences to newvar

perl -i.old -pe 's{\boldvar\b}{newvar}g' *.[chy]

• command-line that reverses the whole file by lines

perl -e 'print reverse <>' file1 file2 file3 ....

• find palindromes

perl -lne 'print if $_ eq reverse' /usr/dict/words

• command-line that reverse all the bytes in a file

perl -0777e 'print scalar reverse <>' f1 f2 f3 ...

• command-line that reverses the whole file by paragraphs

perl -00 -e 'print reverse <>' file1 file2 file3 ....

• increment all numbers found in these files

perl i.tiny -pe 's/(\d+)/ 1 + $1 /ge' file1 file2 ....

• command-line that shows each line with its characters backwards

perl -nle 'print scalar reverse $_' file1 file2 file3 ....

• delete all but lines between START and END

perl -i.old -ne 'print unless /^START$/ .. /^END$/' foo.txt

• binary edit (careful!)

perl -i.bak -pe 's/Mozilla/Slopoke/g' /usr/local/bin/netscape

• look for dup words

perl -0777 -ne 'print "$.: doubled $_\n" while /\b(\w+)\b\s+\b\1\b/gi'

• command-line that prints the last 50 lines (expensively)

perl -e '@lines = <>; print @lines[ $#lines .. $#lines-50' f1 f2 f3 ...

• using the ternary operator:

echo "|E..|"|perl -ne 'printf("%s\n",substr($_,1,1)=~/[A-Z]/?substr($_,1,1):"_");'
# prints "E" if that substr is A-Z
# else prints "_"

External links

• Cultured Perl: One-liners 101
• Cultured Perl: One-liners 102
• Oneliners and other very short programs
• Perl's pearls
• Perl one-liners
• Perl one-liners for the bioinformatician
• Perl One Liners
• Minimal Perl: For UNIX and Linux People