mirror of https://github.com/mkerrisk/man-pages
79 lines
1.9 KiB
Groff
79 lines
1.9 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" Distributed under GPL
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.\" Thanks to glibc info pages
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.\"
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.\" Modified 2003-11-18, aeb: glibc is broken
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.TH GETGROUPLIST 3 2003-11-18 "GNU" "Linux Programmer's Manual"
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.SH NAME
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getgrouplist \- list of groups a user belongs to
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.SH SYNOPSIS
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.sp
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.B #include <grp.h>
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.sp
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.BI "int getgrouplist(const char *" user ", gid_t " group ,
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.in 24
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.BI "gid_t *" groups ", int *" ngroups );
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.SH DESCRIPTION
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The
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.BR getgrouplist ()
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function scans the group database for all the groups
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.I user
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belongs to. Up to
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.RI * ngroups
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group IDs corresponding to these groups are stored in the array
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.IR groups ;
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the return value from the function is the number of group IDs
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actually stored. The group
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.I group
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is automatically included in the list of groups returned by
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.BR getgrouplist ().
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.SH "RETURN VALUE"
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If
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.RI * ngroups
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is smaller than the total number of groups found, then
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.BR getgrouplist ()
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returns a value of `\-1'.
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In all cases the actual number of groups is stored in
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.RI * ngroups .
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.SH BUGS
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The glibc 2.3.2 implementation of this function is broken:
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it overwrites memory when the actual number of groups is larger than
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.RI * ngroups .
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.SH "CONFORMING TO"
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This function is non-standard; it appears on most BSDs.
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.SH "VERSIONS"
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This function is present since glibc 2.2.4.
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.SH EXAMPLE
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.nf
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/* This crashes with glibc 2.3.2 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <grp.h>
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#include <pwd.h>
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int
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main(void)
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{
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int i, ng = 0;
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char *user = "who"; /* username here */
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gid_t *groups = NULL;
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struct passwd *pw = getpwnam(user);
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if (pw == NULL)
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return 0;
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if (getgrouplist(user, pw->pw_gid, NULL, &ng) < 0) {
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groups = (gid_t *) malloc(ng * sizeof (gid_t));
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getgrouplist(user, pw->pw_gid, groups, &ng);
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}
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for(i = 0; i < ng; i++)
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printf("%d\en", groups[i]);
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return 0;
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}
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.fi
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.SH "SEE ALSO"
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.BR getgroups (3),
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.BR setgroups (3)
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