DevTut

# Perl one-liners

# Execute some Perl code from command line

Simple one-liners may be specified as command line arguments to perl using the -e switch (think "execute"):

perl -e'print "Hello, World!\n"'

Due to Windows quoting rules you can't use single-quoted strings but have to use one of these variants:

perl -e"print qq(Hello, World!\n)"
perl -e"print \"Hello, World!\n\""

Note that to avoid breaking old code, only syntax available up to Perl 5.8.x can be used with -e. To use anything newer your perl version may support, use -E instead. E.g. to use say available from 5.10.0 on plus Unicode 6.0 from >=v5.14.0 (also uses -CO to make sure STDOUT prints UTF-8):

perl -CO -E'say "\N{PILE OF POO}"'

# Using double-quoted strings in Windows one-liners

Windows uses only double quotes to wrap command line parameters. In order to use double quotes in perl one-liner (i.e. to print a string with an interpolated variable), you have to escape them with backslashes:

perl -e "my $greeting = 'Hello'; print \"$greeting, world!\n\""

To improve readability, you may use a qq() operator:

perl -e "my $greeting = 'Hello'; print qq($greeting, world!\n)"


perl -ne'print if /foo/' file.txt

Case-insensitive:

perl -ne'print if /foo/i' file.txt

# Replace a substring with another (PCRE sed)

perl -pe"s/foo/bar/g" file.txt

Or in-place:

perl -i -pe's/foo/bar/g' file.txt

On Windows:

perl -i.bak -pe"s/foo/bar/g" file.txt


perl -lane'print "$F[0] $F[-1]"' data.txt
# prints the first and the last fields of a space delimited record

CSV example:

perl -F, -lane'print "$F[0] $F[-1]"' data.csv


perl -ne'print if 5..10' file.txt

# Edit file in-place

Without a backup copy (not supported on Windows (opens new window))

perl -i -pe's/foo/bar/g' file.txt

With a backup copy file.txt.bak

perl -i.bak -pe's/foo/bar/g' file.txt

With a backup copy old_file.txt.orig in the backup subdirectory (provided the latter exists):

perl -i'backup/old_*.orig' -pe's/foo/bar/g' file.txt

# Reading the whole file as a string

perl -0777 -ne'print "The whole file as a string: --->$_<---\n"'

Note: The -0777 is just a convention. Any -0400 and above would de the same.

# Upload file into mojolicious

perl -Mojo -E 'p("http://localhost:3000" => form => {Input_Type => "XML", Input_File => {file => "d:/xml/test.xml"}})'

File d:/xml/test.xml will be uploaded to server which listen connections on localhost:3000 (Source (opens new window))

In this example:

-Mmodule executes use module; before executing your program
-E commandline is used to enter one line of program
If you have no ojo module you can use cpanm ojo command to install it

To read more about how to run perl use perldoc perlrun command or read here (opens new window)

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