4

I have a problem with redirections :

$ which python3

gives me

/Library/Frameworks/Python.framework/Versions/3.7/bin/python3

and

$ ls -l /Library/Frameworks/Python.framework/Versions/3.7/bin/python3

gives me 

lrwxr-xr-x  1 root  admin  9  5 fév 18:30 /Library/Frameworks/Python.framework/Versions/3.7/bin/python3 -> python3.7

but 

which python3 | ls -l

don't gives me the same result.

Do you know why ? And what is the right command for redirection ?

I'm using OSX.

I have to say that the following question pass the output of previous command to next as an argument may be the same as this one, but if I look the answers that were given, there I'm lost. To be useful, they require more advanced knowledge or study than those given here.

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1
  • I've updated the list of duplicates to some other better (IMHO) questions on the same topic. Especially Redirecting the content of a file to the command "echo" mirrors your question quite well as echo behaves like ls with regards to (not) reading its standard input. Commented Feb 16, 2019 at 10:33

3 Answers 3

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13

ls does not take input from standard in, but only from arguments:

Try ls -l "$(which python3)"

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12

ls does not read from the pipe. In fact, ls does not use its standard input at all.

Instead, you have to pass the thing you'd like to run ls -l on via the command line of ls:

ls -l "$( which python3 )"

This uses a command substitution on the command line of ls -l which will expand to the output of the which command. This will then be used as a command line argument for ls.

Alternatively:

ls -l "$( command -v python3 )"

Related:

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8

Other answers are good, but this is also handy:

which python3 | xargs ls -l

xargs gets values from stdin and appends them as command-line argument to the specified program.

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2
  • This is much the best answer in my view, easy to apply to similar and more general cases of command line usage and output redirection. Thanks @jick. Commented Jan 15, 2020 at 10:49
  • This answer doesn't behave weirdly if you're passing quotes " in args, +1 Commented Nov 26, 2021 at 1:19

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