How to pipe information into a buffer to recall in unix shell

I want to know how to pipe t开发者_开发问答ext from a cat or anything so i can use it as a variable.

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If using bash​:

FOO=$(cat foo)

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if using bash, no need cat

var=$(<file)

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i hope i understood you.
u can pipe to stdin with FIRST_COMMAND | SECOND_COMMAND.
if you want to use really variable u should write

$var=`COMMAND`

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Set the variable to the result of a command using ' characters, like this:

$ var='cat foo'

This approach works in most shells.