Input, Output, and Error Redirections

• Input, output, and error character streams:
  • standard input (or stdin)
    • Input redirection
    • <
  • standard output (or stdout)

    • • Append instead of overwrite
    • &>
      • Redirect standard error and output
  • standard error (or stderr)
    • 2>
• File descriptors:
  • 0, 1, and 2
    • 1
      • Represents standard output location
  • Can use these to represent character streams instead of <, and >
• noclobber feature
  • prevent overwriting of the output file
  • set -o noclobber
    • activates the feature
  • set +o noclobber
    • deactivate the feature

[root@localhost ~]# vim test.txt
[root@localhost ~]# set -o noclobber
[root@localhost ~]# echo "Hello" > test.txt
-bash: test.txt: cannot overwrite existing file
[root@localhost ~]# set +o noclobber
[root@localhost ~]# echo "Hello" > test.txt
[root@localhost ~]# cat test.txt
Hello