setnetgrent(3)

💖 setnetgrent(3) — Library Functions Manual 💖

okay bestie, sit down, we're learning netgroups today and honestly? it's giving vintage. this whole page is about setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, and innetgr — the girlies that handle network group entries. and yes, it lives in the Standard C library (libc, -lc). 🎀

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✨ SYNOPSIS ✨

#include <netdb.h>

int setnetgrent(const char *netgroup);
void endnetgrent(void);

int getnetgrent(char **restrict host,
            char **restrict user, char **restrict domain);
int getnetgrent_r(size_t size;
            char **restrict host,
            char **restrict user,
            char **restrict domain,
            char buf[restrict size], size_t size);

int innetgr(const char *netgroup, const char *host,
            const char *user, const char *domain);

🦋 Feature Test Macro Requirements for glibc 🦋

(peep feature_test_macros(7) if you're nosy, and you should be)

setnetgrent(), endnetgrent(), getnetgrent(), getnetgrent_r(), innetgr():

• Since glibc 2.19:
  • _DEFAULT_SOURCE
• glibc 2.19 and earlier:
  • _BSD_SOURCE || _SVID_SOURCE

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🌸 DESCRIPTION 🌸

The netgroup is a SunOS invention. no cap, that's literally where it came from. A netgroup database is a list of string triples — that's (hostname, username, domainname) — or other netgroup names. Any of the elements in a triple can be empty, and empty means ✨anything matches✨. The functions described here allow access to the netgroup databases. And the file /etc/nsswitch.conf is the one that defines what database is searched. 👑

The setnetgrent() call defines the netgroup that will be searched by subsequent getnetgrent() calls. The getnetgrent() function retrieves the next netgroup entry, and returns pointers in host, user, domain. A null pointer means that the corresponding entry matches any string — wildcard behavior, we love her 💅. The pointers are valid only as long as there is no call to other netgroup-related functions. To avoid this problem you can use the GNU function getnetgrent_r() that stores the strings in the supplied buffer. To free all allocated buffers use endnetgrent(). 🧹

In most cases you want to check only if the triplet (hostname, username, domainname) is a member of a netgroup. The function innetgr() can be used for this without calling the above three functions — shortcut queen 🫶. Again, a null pointer is a wildcard and matches any string. The function is thread-safe. 🔥

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💜 RETURN VALUE 💜

These functions return 1 on success and 0 for failure. that's it, that's the whole vibe. ✨

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🍓 FILES 🍓

• /etc/netgroup
• /etc/nsswitch.conf

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🌈 ATTRIBUTES 🌈

For an explanation of the terms used in this section, see attributes(7).

• setnetgrent(), getnetgrent_r(), innetgr() — Thread safety: MT-Unsafe race:netgrent locale
• endnetgrent() — Thread safety: MT-Unsafe race:netgrent
• getnetgrent() — Thread safety: MT-Unsafe race:netgrent race:netgrentbuf locale

In the above table, netgrent in race:netgrent signifies that if any of the functions setnetgrent(), getnetgrent_r(), innetgr(), getnetgrent(), or endnetgrent() are used in parallel in different threads of a program, then data races could occur.

😭 bestie PLEASE heed this one. parallel calls in different threads → data races. it's giving chaos and we do not want that energy in your program.

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⭐ VERSIONS ⭐

In the BSD implementation, setnetgrent() returns void. (different flavor, different rules, iykyk)

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🎀 STANDARDS 🎀

None. literally none. it's giving "we made this up and it stuck". 💀

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👑 HISTORY 👑

setnetgrent(), endnetgrent(), getnetgrent(), and innetgr() are available on most UNIX systems. getnetgrent_r() is not widely available on other systems — she's the rare one, the main character of portability. 🦋

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🔥 SEE ALSO 🔥

• sethostent(3)
• setprotoent(3)
• setservent(3)

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and that's the whole page, bestie!! you ate this. this was Linux man-pages 6.20, dated 2026-02-08 — so when you're citing your sources, that's the icon right there. mwah 💖✨🎀