Just enough perl to do most everything! Tom Christianson (spelling?)
once posted a canonical list of one line perl programs to do many common
command-line tasks.
It included:
# 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 $_' file1 file2 file3 ....
# delete all but lines beween START and END
perl -i.old -ne 'print unless /^START$/ .. /^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 ...
