perl famous oneliners cheat sheet

# File:PerlOneLiners.sh v.1.1.0 

perl -p -i -e 's/oldstring/newstring/g'

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

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

# 2. delete first 10 lines

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

# 3. change all the isolated oldvar occurrences to newvar

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

# 4. increment all numbers found in these files

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

# 5. delete all but lines between START and END

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

# 6. binary edit (careful!)

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

# 1. command-line that reverses the whole input by lines

#    (printing each line in reverse order)

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

# 2. command-line that shows each line with its characters backwards

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

# 3. find palindromes in the /usr/dict/words dictionary file

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

# 4. command-line that reverses all the bytes in a file

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

# 5. command-line that reverses each paragraph in the file but prints

#    them in order

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

# 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 ...

# find /cygdrive/c/Temp/nmo/nmo.1.2.0.prod.ysg -type f | xargs perl -pi -e 's/\r\n/\n/g'

# find /cygdrive/c/Temp/nmo/nmo.1.2.0.prod.ysg -type f -name '*.bak' | xargs rm -f

# how-to sort files based on a number sequence in their file names

# list dir files , grap a number from their names , print with NumberFileName, sort , print finally the names without the Number but sorted 

ls -1 | perl -ne 'm/(\d{8})/; print $1 . $_ ;' | sort -nr | perl -ne 's/(\d{8)//;print $_'

# how-to remove all blank lines 

perl -ne 'print unless /^$/'

# how-to number all lines in a file

cat tmp.txt | perl -pe '$_ = "$. $_"'

#how-to print the numbers from 1 till 20 on each line 

perl -le 'print join "\n", (1..20)'

#how-to create a file with standar row length

cat tmp.txt | perl -ne 'chomp($_); print $_ . " " . "a"x(50-length($_)) . "\n"'

# how-to convert a list of numeric ASCII values into a string

perl -le '@ascii = (7, 111, 100, 105, 110, 103); print pack("C*", @ascii)'

# how-to print the Unix time

# Print UNIX time (seconds since Jan 1, 1970, 00:00:00 UTC)

perl -le 'print time'

# how-to convert all text to uppercase

perl -nle 'print uc'

perl -ple '$_=uc'

perl -nle 'print "\U$_"'

# how-to convert all text to lowercase

perl -nle 'print lc'

perl -ple '$_=lc'

perl -nle 'print "\L$_"'

# Camel case each line

perl -ple 's/(\w+)/\u$1/g'

perl -ple 's/(?<!['])(\w+)/\u\1/g'

#'

# Strip leading whitespace (spaces, tabs) from the beginning of each line

perl -ple 's/^[ \t]+//'

perl -ple 's/^\s+//'

# Strip trailing whitespace (space, tabs) from the end of each line

perl -ple 's/[ \t]+$//'

# Strip whitespace from the beginning and end of each line

perl -ple 's/^[ \t]+|[ \t]+$//g'

# Convert UNIX newlines to DOS/Windows newlines

perl -pe 's|\n|\r\n|'

# Purpose:

# to provide a cheat sheet for famous perl one liners

# VersionHistory: 

# 1.1.0 --- added famous perl one liners 

# 1.0.0 --- Initial creation

# sources:

# http://www.catonmat.net/blog/perl-one-liners-explained-part-one/