According to
style(9),
it is not a good practice to call
exit(3)
with arbitrary values to indicate a failure condition when ending
a program.
Instead, the pre-defined exit codes from
should be used, so the caller of the process can get a rough
estimation about the failure class without looking up the source code.
The successful exit is always indicated by a status of 0, or
EX_OK
Error numbers begin at
EX__BASE
to reduce the possibility of clashing with other exit statuses that
random programs may already return.
The meaning of the codes is
approximately as follows:
EX_USAGE (64)
The command was used incorrectly, e.g., with the wrong number of
arguments, a bad flag, a bad syntax in a parameter, or whatever.
EX_DATAERR (65)
The input data was incorrect in some way.
This should only be used
for user's data and not system files.
EX_NOINPUT (66)
An input file (not a system file) did not exist or was not readable.
This could also include errors like
``message
''
to a mailer (if it cared to catch it).
EX_NOUSER (67)
The user specified did not exist.
This might be used for mail
addresses or remote logins.
EX_NOHOST (68)
The host specified did not exist.
This is used in mail addresses or
network requests.
EX_UNAVAILABLE (69)
A service is unavailable.
This can occur if a support program or file
does not exist.
This can also be used as a catchall message when
something you wanted to do does not work, but you do not know why.
EX_SOFTWARE (70)
An internal software error has been detected.
This should be limited
to non-operating system related errors as possible.
EX_OSERR (71)
An operating system error has been detected.
This is intended to be
used for such things as
``cannot fork''
``cannot create pipe''
or the like.
It includes things like getuid returning a user that
does not exist in the passwd file.
EX_OSFILE (72)
Some system file (e.g.,
/etc/passwd
/var/run/utmp
etc.) does not exist, cannot be opened, or has some sort of error
(e.g., syntax error).
EX_CANTCREAT (73)
A (user specified) output file cannot be created.
EX_IOERR (74)
An error occurred while doing I/O on some file.
EX_TEMPFAIL (75)
Temporary failure, indicating something that is not really an error.
In sendmail, this means that a mailer (e.g.) could not create a
connection, and the request should be reattempted later.
EX_PROTOCOL (76)
The remote system returned something that was
``not possible''
during a protocol exchange.
EX_NOPERM (77)
You did not have sufficient permission to perform the operation.
This
is not intended for file system problems, which should use
EX_NOINPUT
or
EX_CANTCREAT
but rather for higher level permissions.
EX_CONFIG (78)
Something was found in an unconfigured or misconfigured state.
The numerical values corresponding to the symbolical ones are given in
parenthesis for easy reference.
