A Shell Can Read a Script from Its Standard Input, but... (Unix Power Tools, 3rd Edition)

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36.17. 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 stdin-demo script:

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

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

-- CT


36.16. n>&m: Swap Standard Output and Standard Error		36.18. Shell Scripts On-the-Fly from Standard Input