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This is the BSDA Study Guide Book written via a wiki collaboration. This is a work in progress. You may contribute to or discuss this specific page at http://bsdwiki.reedmedia.net/wiki/Demonstrate_proficiency_in_using_redirection__44___pipes_and_tees.html.
Demonstrate proficiency in using redirection, pipes and tees
Be able to to redirect standard input, output or error, use a pipe to send the output of one command to another command or file, and use a tee to copy standard input to standard output.
tee: pipe fitting, this utility copies standard input to standard output, making a copy in zero or more files. The output is unbuffered.
file descriptors (fd):
fd 0: stdin
fd 1: stdout
fd 2: stderr
<: redirect stdin of a process so that input is read from a file instead of from the keyboard
command < infile
>: redirects stdout to a file
command > outfile
>>: appends stdout to a file
command >> outfile
| : piping command output to another command
command1 | command2 | ... | commandN
tee: lets you divert a copy of the data passing between commands to a file without changing how the pipeline functions
who | tee savewho | wc -l
>&: temporarily connect something to something else
ls 2>&1 means temporarily connect stderr to stdout
<, >, |, tee(1), >\& and |\&