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Redirects and Pipes

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Redirects and Pipes#

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  • stdout (1)

  • stderr (2)

Redirects#

$ grep root /etc/passwd /etc/shadow
/etc/passwd:root:x:0:0:root:/root:/bin/bash
/etc/passwd:operator:x:11:0:operator:/root:/sbin/nologin
grep: /etc/shadow: Permission denied

$ grep root /etc/passwd /etc/shadow > /tmp/file.txt
grep: /etc/shadow: Permission denied

$ grep root /etc/passwd /etc/shadow 2> /tmp/error.txt
/etc/passwd:root:x:0:0:root:/root:/bin/bash
/etc/passwd:operator:x:11:0:operator:/root:/sbin/nologin

$ grep root /etc/passwd /etc/shadow > /tmp/file.txt 2> /tmp/error.txt

$ grep root /etc/passwd /etc/shadow > /tmp/file.txt 2>&1

$ grep root /etc/passwd /etc/shadow 2> /tmp/error.txt 1>&2

$ ( cat /etc/passwd /etc/shadow | grep root ) > /tmp/file.txt

$ ( cat /etc/passwd /etc/shadow | grep root ) 2> /dev/null

Pipes#

$ cat /etc/passwd | grep root
root:x:0:0:root:/root:/bin/bash

$ cat /etc/passwd | grep root | wc -l
1

$ cat /etc/passwd | grep -v '^#' | cut -d: -f1 | sort | uniq
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