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Shell Programming for the Initiated
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45.24 A Shell Can Read a Script from its Standard Input, But...

Q: What is the difference between sh < file and sh file?

A: The first way keeps the script from reading anything else from its input. Consider the zip script:

A:

while read word
do   echo $word | sed s/foo/bar/
done

If run as sh zip, it will read from your terminal, replacing foo with bar. If run as sh < zip, it will exit right away, since after reading the script, there's no input left.

- CT in net.unix on Usenet, 29 December 1984


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