DESCRIPTION
It is not a good practice to call
exit(3) with arbitrary values to indicate a failure condition when ending a program. In addition to the two standard constants in
<stdlib.h>,
EXIT_SUCCESS and
EXIT_FAILURE, the header
<sysexits.h> defines few exit codes that can be used as a parameter to the
exit(3) function. By using these constants 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 “No 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.