I want to run a Ruby/Python one-liner in a shell script, like:
python 'print "hello world"'
or
ruby 'puts "hello world"'
or something like that so I can quickly pipe the input elsewhere.
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7 Answers
Since version 2.05b, bash can redirect standard input (stdin) from a "here string" using the <<< operator.
$ python <<< 'print "hello world"'
hello world
$ ruby <<< 'puts "hello world"'
hello world
1 Comment
the wolf
One of the only answers with a unique answer. Thanks
Each of these commands has a switch to execute a string passed as an argument. For python, it's -c:
$ python -c 'print "hello world"'
hello world
For ruby, it's -e:
$ ruby -e 'puts "hello world"'
hello world
By the way, the output of python --help, ruby --help or looking in the man page for either program would give you the answer.
Comments
Use the argument to the interpreter that tells it that the next argument is code to be run.
python -c 'print "hello world"'
answered Sep 22, 2015 at 6:03
Ignacio Vazquez-Abrams
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Comments
For Ruby:
ruby -e 'puts "Hello world"'
answered Sep 22, 2015 at 6:06
Alexander Shlenchack
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In Perl, from command line:
perl -e 'print "Hello World\n";'
Or inside bash script:
#!/bin/bash
perl -e 'print "Hello World\n";'
1 Comment
simbabque
You can also save two characters and go
perl -E 'say "Hello World"'. You don't need the ; at all. Actually OP was not asking for a line break though.If you mean using a one liner of perl/awk/python in a pipe, it is just like most other Unix utilities:
$ python -c 'print "hello"' | tr "[a-z]" "[A-Z]"
HELLO
$ ruby -e 'puts "hello"' | tr "[a-z]" "[A-Z]"
HELLO
$ python -c 'print "GREETINGS"' | perl -lpe 's/([EI])/lc($1)/ge'
GReeTiNGS
5 Comments
the wolf
Seems kinda harsh to vote this down given the votes on the other answers here.
simbabque
Printing from Python to pipe to Perl to use regex! :-)
the wolf
@sawa: what are you saying? Posts should be judged not just on what they say but what they used to say???
sawa
@thewolf [W]hat are you saying? Votes should foresee the future edit[?]
the wolf
I suppose not being one who down votes often I think it does make sense to change the vote if the original reason is no longer there. I personally only down vote if a) the answer is wrong and b) someone does not change it if given a chance.
You need neither Perl, Python or Ruby to pipe a fixed string to another application. The echo program can be used for that.
$ echo 'foo' | cat
foo
See explainshell.com for more infos.