sysexits.h(3head)

💅 sysexits.h — exit codes for programs

okay bestie, pull up a chair 🪑 because this is the <sysexits.h> page, from section 3head, and honestly? it's the blueprint for ✨how a program tells you what went wrong✨. exit codes, but make them mean something. no more mysterious 1s. periodt.

---

📚 LIBRARY

Standard C library (libc) 🫶

---

✨ SYNOPSIS ✨

like, here's the whole vibe, verbatim, no cap:

#include <sysexits.h>
#define EX_OK           0    /* successful termination */

#define EX__BASE        64   /* base value for error messages */

#define EX_USAGE        64   /* command line usage error */
#define EX_DATAERR      65   /* data format error */
#define EX_NOINPUT      66   /* cannot open input */
#define EX_NOUSER       67   /* addressee unknown */
#define EX_NOHOST       68   /* host name unknown */
#define EX_UNAVAILABLE  69   /* service unavailable */
#define EX_SOFTWARE     70   /* internal software error */
#define EX_OSERR        71   /* system error (e.g., can't fork) */
#define EX_OSFILE       72   /* critical OS file missing */
#define EX_CANTCREAT    73   /* can't create (user) output file */
#define EX_IOERR        74   /* input/output error */
#define EX_TEMPFAIL     75   /* temp failure; user is invited to retry
                                */
#define EX_PROTOCOL     76   /* remote error in protocol */
#define EX_NOPERM       77   /* permission denied */
#define EX_CONFIG       78   /* configuration error */

#define EX__MAX         ...  /* maximum listed value */

look at all those little constants 🎀 they're all just macros, they cost you nothing at runtime, and they make your program legible. we love a free glow-up 💖

---

🦋 DESCRIPTION

so, a few programs exit with these following error codes. that's the whole premise. 💁

The successful exit is always indicated by a status of 0, aka EX_OK (which is the same thing as EXIT_SUCCESS from <stdlib.h> — they're besties, they're literally the same). 😌

Error numbers begin at EX__BASE so there's less chance of clashing with other exit statuses that random programs might already be returning. like, the low numbers were taken, okay?? 😭 so we start at 64 and go up from there. iconic behavior honestly.

The meaning of the code is approximately as follows:

• EX_USAGE — the command was used incorrectly, i.e. wrong number of arguments, a bad flag, bad syntax in a parameter, or whatever. you fumbled the invocation, bestie. 🙈
• EX_DATAERR — the input data was incorrect in some way. only use this for the user's data, not for system files. user data problems get user data codes. 💅
• EX_NOINPUT — an input file (not a system file!) didn't exist or wasn't readable. this could also cover errors like "No message" to a mailer (if it even cared to catch it). 👀
• EX_NOUSER — the user you specified didn't exist. this might be used for mail addresses or remote logins. that person? not real. 💀
• EX_NOHOST — the host you specified didn't exist. this one is used in mail addresses or network requests. 🛰️
• EX_UNAVAILABLE — a service is unavailable. happens if a support program or file doesn't exist. this one is also the catch-all for when something you wanted to do just... doesn't work, and you genuinely don't know why. the "idk it's giving broken" code 🫠
• EX_SOFTWARE — an internal software error has been detected. if possible, keep this limited to non-operating-system-related errors. it's a you problem, not a kernel problem, iykyk.
• EX_OSERR — an operating system error has been detected. this is intended for stuff like "cannot fork", "cannot create pipe", or the like. it also includes things like getuid(2) returning a user that doesn't exist in the passwd(5) file. 😵 the OS itself is acting up.
• EX_OSFILE — some system file (e.g. /etc/passwd, /etc/utmp, etc.) doesn't exist, can't be opened, or has some sort of error (e.g. a syntax error). 📁 missing/broken system file energy.
• EX_CANTCREAT — a (user-specified) output file cannot be created. the write just isn't writing. 😭
• EX_IOERR — an error occurred while doing I/O on some file. something went sideways mid-read or mid-write. 🍓
• EX_TEMPFAIL — temporary failure, indicating something that isn't really an error. for example, a mailer couldn't create a connection, and the request should be reattempted later. try again later, it's not you it's the moment ✨
• EX_PROTOCOL — the remote system returned something that was "not possible" during a protocol exchange. the other side said something that literally cannot happen. rude. 😤
• EX_NOPERM — you didn't have sufficient permission to perform the operation. not intended for file system problems — those should use EX_NOINPUT or EX_CANTCREAT — but rather for higher level permissions. know the difference, bestie. 👑
• EX_CONFIG — something was found in an unconfigured or misconfigured state. the config file ate and left no crumbs (complimentary? no. it's broken). 🧚

The numerical values corresponding to the symbolical ones are given in parenthesis for easy reference. like a little cheat sheet, built right in. 🎀

---

📏 STANDARDS

BSD. 📜 that's it, that's the standard.

---

🕰️ HISTORY

The <sysexits.h> file appeared in 4.0BSD for use by the deliverymail utility, which was later renamed to sendmail(8). so it's genuinely a nepo baby of the mail world 💌 and it's been serving ever since.

---

⚠️ CAVEATS

The choice of an appropriate exit value is often ambiguous. 😭 fr fr. you'll be staring at EX_SOFTWARE vs EX_OSERR at 3am like... which one am i. nobody knows. vibe check failed.

---

👀 SEE ALSO

• err(3)
• error(3)
• exit(3)

---

and that's the whole page, bestie — go forth and exit meaningfully 💖🦋✨

this was sysexits.h(3head) from Linux man-pages 6.20, dated 2026-10-11 🌈 slay, stay iconic, and always #include <sysexits.h> 👑💅