GETSPNAM(3C) Standard C Library Functions GETSPNAM(3C)


NAME


getspnam, getspnam_r, getspent, getspent_r, setspent, endspent,
fgetspent, fgetspent_r - get password entry

SYNOPSIS


#include <shadow.h>

struct spwd *getspnam(const char *name);


struct spwd *getspnam_r(const char *name, struct spwd *result,
char *buffer, int buflen);


struct spwd *getspent(void);


struct spwd *getspent_r(struct spwd *result, char *buffer,
int buflen);


void setspent(void);


void endspent(void);


struct spwd *fgetspent(FILE *fp);


struct spwd *fgetspent_r(FILE *fp, struct spwd *result,
char *buffer, int buflen);


DESCRIPTION


These functions are used to obtain shadow password entries. An entry may
come from any of the sources for shadow specified in the
/etc/nsswitch.conf file (see nsswitch.conf(4)).


The getspnam() function searches for a shadow password entry with the
login name specified by the character string argument name.


The setspent(), getspent(), and endspent() functions are used to
enumerate shadow password entries from the database.


The setspent() function sets (or resets) the enumeration to the beginning
of the set of shadow password entries. This function should be called
before the first call to getspent(). Calls to getspnam() leave the
enumeration position in an indeterminate state.


Successive calls to getspent() return either successive entries or NULL,
indicating the end of the enumeration.


The endspent() function may be called to indicate that the caller expects
to do no further shadow password retrieval operations; the system may
then close the shadow password file, deallocate resources it was using,
and so forth. It is still allowed, but possibly less efficient, for the
process to call more shadow password functions after calling endspent().


The fgetspent() function, unlike the other functions above, does not use
nsswitch.conf; it reads and parses the next line from the stream fp,
which is assumed to have the format of the shadow file (see shadow(4)).

Reentrant Interfaces


The getspnam(), getspent(), and fgetspent() functions use thread-
specific data storage that is reused in each call to one of these
functions by the same thread, making them safe to use but not recommended
for multithreaded applications.


The getspnam_r(), getspent_r(), and fgetspent_r() functions provide
reentrant interfaces for these operations.


Each reentrant interface performs the same operation as its non-reentrant
counterpart, named by removing the _r suffix. The reentrant interfaces,
however, use buffers supplied by the caller to store returned results,
and are safe for use in both single-threaded and multithreaded
applications.


Each reentrant interface takes the same argument as its non-reentrant
counterpart, as well as the following additional arguments. The result
argument must be a pointer to a struct spwd structure allocated by the
caller. On successful completion, the function returns the shadow
password entry in this structure. The buffer argument must be a pointer
to a buffer supplied by the caller. This buffer is used as storage space
for the shadow password data. All of the pointers within the returned
struct spwd result point to data stored within this buffer (see RETURN
VALUES). The buffer must be large enough to hold all of the data
associated with the shadow password entry. The buflen argument should
give the size in bytes of the buffer indicated by buffer.


For enumeration in multithreaded applications, the position within the
enumeration is a process-wide property shared by all threads. The
setspent() function may be used in a multithreaded application but resets
the enumeration position for all threads. If multiple threads interleave
calls to getspent_r(), the threads will enumerate disjoint subsets of the
shadow password database.


Like its non-reentrant counterpart, getspnam_r() leaves the enumeration
position in an indeterminate state.

RETURN VALUES


Password entries are represented by the struct spwd structure defined in
<shadow.h>:

struct spwd{
char *sp_namp; /* login name */
char *sp_pwdp; /* encrypted passwd */
int sp_lstchg; /* date of last change */
int sp_min; /* min days to passwd change */
int sp_max; /* max days to passwd change*/
int sp_warn; /* warning period */
int sp_inact; /* max days inactive */
int sp_expire; /* account expiry date */
unsigned int sp_flag; /* not used */
};


See shadow(4) for more information on the interpretation of this data.


The getspnam()and getspnam_r() functions each return a pointer to a
struct spwd if they successfully locate the requested entry; otherwise
they return NULL.


The getspent(), getspent_r(), fgetspent(), and fgetspent() functions
each return a pointer to a struct spwd if they successfully enumerate an
entry; otherwise they return NULL, indicating the end of the enumeration.


The getspnam(), getspent(), and fgetspent() functions use thread-
specific data storage, so returned data must be copied before a
subsequent call to any of these functions if the data is to be saved.


When the pointer returned by the reentrant functions getspnam_r(),
getspent_r(), and fgetspent_r() is non-null, it is always equal to the
result pointer that was supplied by the caller.

ERRORS


The reentrant functions getspnam_r(), getspent_r(), and fgetspent_r()
will return NULL and set errno to ERANGE if the length of the buffer
supplied by caller is not large enough to store the result. See Intro(2)
for the proper usage and interpretation of errno in multithreaded
applications.

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+---------------+----------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+----------------------------+
|MT-Level | See "Reentrant Interfaces" |
| | in DESCRIPTION. |
+---------------+----------------------------+

SEE ALSO


passwd(1), yppasswd(1), Intro(3), getlogin(3C), getpwnam(3C),
nsswitch.conf(4), passwd(4), shadow(4), attributes(5)

WARNINGS


The reentrant interfaces getspnam_r(), getspent_r(), and fgetspent_r()
are included in this release on an uncommitted basis only, and are
subject to change or removal in future minor releases.

NOTES


When compiling multithreaded applications, see Intro(3), Notes On
Multithreaded Applications, for information about the use of the
_REENTRANT flag.


Use of the enumeration interfaces getspent() and getspent_r() is not
recommended; enumeration is supported for the shadow file and NIS but in
general is not efficient and may not be supported for all database
sources. The semantics of enumeration are discussed further in
nsswitch.conf(4).


Access to shadow password information may be restricted in a manner
depending on the database source being used. Access to the /etc/shadow
file is generally restricted to processes running with the effective uid
of the file owner or the {PRIV_FILE_DAC_READ} privilege. Other database
sources may impose stronger or less stringent restrictions.


Empty fields in the database source return -1 values for all fields
except sp_pwdp and sp_flag, where the value returned is 0.


When NIS is used as the database source, the information for the shadow
password entries is obtained from the ``passwd.byname'' map. This map
stores only the information for the sp_namp and sp_pwdp fields of the
struct spwd structure. Shadow password entries obtained from NIS will
contain the value -1 in the remainder of the fields.


February 25, 2017 GETSPNAM(3C)