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2012-03-22

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/
 

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