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| Standard C Library Functions | getspnam(3C) |
| | getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fgetspent, fgetspent_r - get password entry |
SYNOPSIS
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#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); |
| | struct spwd *fgetspent(FILE *fp); |
| | struct spwd *fgetspent_r(FILE *fp, struct spwd *result, char *buffer, int buflen); |
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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
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The getspnam(), getspent(), and fgetspent() functions use static storage that is re-used in each call, making these routines unsafe for use
in 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.
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Password entries are represented by the struct spwd structure defined in <shadow.h>:
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struct spwd{
char *sp_namp; /* login name */
char *sp_pwdp; /* encrypted passwd */
long sp_lstchg; /* date of last change */
long sp_min; /* min days to passwd change */
long sp_max; /* max days to passwd change*/
long sp_warn; /* warning period */
long sp_inact; /* max days inactive */
long sp_expire; /* account expiry date */
unsigned long sp_flag; /* not used */
};
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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 static 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.
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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.
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Applications that use the interfaces described on this manual page cannot be linked statically, since the implementations of these functions employ dynamic loading and linking of shared objects at
run time.
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See attributes(5) for descriptions of the following
attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | See "Reentrant Interfaces" in DESCRIPTION. |
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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.
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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, NIS,
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 as the super-user (root). Other database sources may impose stronger or less stringent restrictions.
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.
When NIS+ is used as the database source, and the caller lacks the permission needed to retrieve the encrypted password from the NIS+
``passwd.org_dir'' table, the NIS+ service returns the string ``*NP*'' instead of the actual encrypted password string. The functions described on this page will then return
the string ``*NP*'' to the caller as the value of the member sp_pwdp in the returned shadow password structure.
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