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LOGIN_CAP(3) NetBSD Library Functions Manual LOGIN_CAP(3)
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by Kimmo Suominen.
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login_getclass, login_getcapbool, login_getcapnum, login_getcapsize,
login_getcapstr, login_getcaptime, login_getpwclass, login_close,
setclasscontext, setusercontext -- query login.conf database about a user
System Utilities Library (libutil, -lutil)
login_getcapbool(login_cap_t *lc, const char *cap, unsigned int def);
login_getcapnum(login_cap_t *lc, const char *cap, quad_t def,
login_getcapsize(login_cap_t *lc, const char *cap, quad_t def,
login_getcapstr(login_cap_t *lc, const char *cap, char *def, char *err);
login_getcaptime(login_cap_t *lc, const char *cap, quad_t def,
login_getpwclass(struct passwd *pwd);
setclasscontext(const char *class, unsigned int flags);
setusercontext(login_cap_t *lc, const struct passwd *pwd, uid_t uid,
unsigned int flags);
The login_getclass() function extracts the entry specified by class (or
default if class is NULL or the empty string) from /etc/login.conf (see
login.conf(5)). If the entry is found, a login_cap_t pointer is
returned. NULL is returned if the user class is not found. When the
login_cap_t structure is no longer needed, it should be freed by the
The login_getpwclass() function is equivalent to:
login_getclass(pwd ? pwd->pw_class : NULL)
Once lc has been returned by login_getclass(), any of the other login_*()
functions may be called.
The login_getcapnum(), login_getcapsize(), login_getcapstr(), and
login_getcaptime() functions all query the database entry for a field
named cap. If the field is found, its value is returned. If the field
is not found, the value specified by def is returned. If an error is
encountered while trying to find the field, err is returned. See
login.conf(5) for a discussion of the various textual forms the value may
take. The login_getcapbool() function is slightly different. It returns
def if no capabilities were found for this class (typically meaning that
the default class was used and the /etc/login.conf file is missing). It
returns a non-zero value if cap, with no value, was found, zero other-
The setclasscontext() function takes class, the name of a user class, and
sets the resources defined by that class according to flags. Only the
LOGIN_SETPATH, LOGIN_SETPRIORITY, LOGIN_SETRESOURCES, and LOGIN_SETUMASK
bits are used. (See setusercontext() below). It returns 0 on success
and -1 on failure.
The setusercontext() function sets the resources according to flags. The
lc argument, if not NULL, contains the class information that should be
used. The pwd argument, if not NULL, provides information about the
user. Both lc and pwd cannot be NULL. The uid argument is used in place
of the user id contained in the pwd structure when calling setuid(2).
The various bits available to be or-ed together to make up flags are:
LOGIN_SETGID Set the group id. Requires the pwd field be speci-
LOGIN_SETGROUPS Set the group membership list by calling
initgroups(3). Requires the pwd field be speci-
LOGIN_SETGROUP Set the group id and call initgroups(3). Requires
the pwd field be specified.
LOGIN_SETLOGIN Sets the login name by setlogin(2). Requires the
pwd field be specified.
LOGIN_SETPATH Sets the PATH environment variable.
LOGIN_SETPRIORITY Sets the priority by setpriority(2).
LOGIN_SETRESOURCES Sets the various system resources by setrlimit(2).
LOGIN_SETUMASK Sets the umask by umask(2).
LOGIN_SETUSER Sets the user id to uid by setuid(2).
LOGIN_SETENV Sets the environment variables as defined by the
setenv keyword, by setenv(3).
LOGIN_SETALL Sets all of the above.
setlogin(2), setpriority(2), setrlimit(2), setuid(2), umask(2),
initgroups(3), secure_path(3), login.conf(5)
The login_getclass family of functions are largely based on the BSD/OS
implementation of same, and appeared in NetBSD 1.5 by kind permission.
The string returned by login_getcapstr() is allocated via malloc(3) when
the specified capability is present and thus it is the responsibility of
the caller to free() this space. However, if the capability was not
found or an error occurred and def or err (whichever is relevant) are
non-NULL the returned value is simply what was passed in to
login_getcapstr(). Therefore it is not possible to blindly free() the
return value without first checking it against def and err.
The same warnings set forth in setlogin(2) apply to setusercontext() when
the LOGIN_SETLOGIN flag is used. Specifically, changing the login name
affects all processes in the current session, not just the current
process. See setlogin(2) for more information.
NetBSD 9.3 June 20, 2013 NetBSD 9.3