getnetgrent(3)
NAME
setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle network group entries
SYNOPSIS
#include <netdb.h>
int setnetgrent(const char *netgroup);
void endnetgrent(void);
int getnetgrent(char **host, char **user, char **domain);
int getnetgrent_r(char **host, char **user,
char **domain, char *buf, size_t buflen);
int innetgr(const char *netgroup, const char *host,
const char *user, const char *domain);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
setnetgrent(), endnetgrent(), getnetgrent(), getnetgrent_r(),
innetgr():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
The netgroup is a SunOS invention. A netgroup database is a list of string triples (hostname, username, domainname) or other netgroup names. Any of the elements in a triple can be empty, which means that anything matches. The functions described here allow access to the netgroup databases. The file /etc/nsswitch.conf 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. 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. Again, a null pointer is a wildcard and matches any string. The function is thread-safe.
RETURN VALUE
These functions return 1 on success and 0 for failure.
FILES
/etc/netgroup /etc/nsswitch.conf
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). ┌─────────────────┬───────────────┬─────────────────────────┐ │Interface │ Attribute │ Value │ ├─────────────────┼───────────────┼─────────────────────────┤ │setnetgrent(), │ Thread safety │ MT-Unsafe race:netgrent │ │getnetgrent_r(), │ │ locale │ │innetgr() │ │ │ ├─────────────────┼───────────────┼─────────────────────────┤ │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.
CONFORMING TO
These functions are not in POSIX.1, but setnetgrent(), endnetgrent(), getnetgrent(), and innetgr() are available on most UNIX systems. getnetgrent_r() is not widely available on other systems.
NOTES
In the BSD implementation, setnetgrent() returns void.
SEE ALSO
sethostent(3), setprotoent(3), setservent(3)
COLOPHON
This page is part of release 4.09 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
