coreutils: Exit status

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1 2.1 Exit status
1 ===============
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1 Nearly every command invocation yields an integral “exit status” that
1 can be used to change how other commands work.  For the vast majority of
1 commands, an exit status of zero indicates success.  Failure is
1 indicated by a nonzero value—typically ‘1’, though it may differ on
1 unusual platforms as POSIX requires only that it be nonzero.
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1    However, some of the programs documented here do produce other exit
1 status values and a few associate different meanings with the values ‘0’
1 and ‘1’.  Here are some of the exceptions: ‘chroot’, ‘env’, ‘expr’,
1 ‘nice’, ‘nohup’, ‘numfmt’, ‘printenv’, ‘sort’, ‘stdbuf’, ‘test’,
1 ‘timeout’, ‘tty’.
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