Saturday, May 26, 2012

Linux 12 - Streams, Pipes and Redirects

  • - stdin
  • - stdout
  • - stderr
  • - tee
  • - xargs

stuff a program chews up

wc < file1.txt
some programs don’t accept data from stdin

stuff a program spits out

ls > ls.txt

ls 1> ls.txt

where a program complains

ls bob 2> ls.txt
redirects stderr to ls.txt


Both stdout and stderror go to the console

To keep a log you would like to:

ls >> ls.txt→ will append
ls bob 2>> ls.txt→ will append stderr

ls bob >> results.txt 2>> errors.txt→ redirects both to files
ls bob > output.txt 2>&1→ redirect stderr to stdout in the same place


not all applications support stdin from other applications

ls | grep 3


- write a program see what is doing and write to a file

- read from std input and write to standard output and file

ls | tee output.txt


- ls | echo

echo does not accept input from ls

- ls | xargs echo






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