mirror of https://github.com/mkerrisk/man-pages
149 lines
4.7 KiB
Plaintext
149 lines
4.7 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "GETPWNAM" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" getpwnam
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.SH NAME
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getpwnam, getpwnam_r \- search user database for a name
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.SH SYNOPSIS
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.LP
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\fB#include <pwd.h>
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.br
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.sp
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struct passwd *getpwnam(const char *\fP\fIname\fP\fB);
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.br
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\fP
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.LP
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\fBint getpwnam_r(const char *\fP\fIname\fP\fB, struct passwd *\fP\fIpwd\fP\fB,
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char
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*\fP\fIbuffer\fP\fB,
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.br
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\ \ \ \ \ \ size_t\fP \fIbufsize\fP\fB, struct passwd **\fP\fIresult\fP\fB);
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\fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIgetpwnam\fP() function shall search the user database for an
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entry with a matching \fIname\fP.
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.LP
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The \fIgetpwnam\fP() function need not be reentrant. A function that
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is not required to be reentrant is not required to be
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thread-safe.
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.LP
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Applications wishing to check for error situations should set \fIerrno\fP
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to 0 before calling \fIgetpwnam\fP(). If
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\fIgetpwnam\fP() returns a null pointer and \fIerrno\fP is non-zero,
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an error occurred.
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.LP
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The \fIgetpwnam_r\fP() function shall update the \fBpasswd\fP structure
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pointed to by \fIpwd\fP and store a pointer to that
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structure at the location pointed to by \fIresult\fP. The structure
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shall contain an entry from the user database with a matching
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\fIname\fP. Storage referenced by the structure is allocated from
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the memory provided with the \fIbuffer\fP parameter, which is
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\fIbufsize\fP bytes in size. The maximum size needed for this buffer
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can be determined with the {_SC_GETPW_R_SIZE_MAX} \fIsysconf\fP()
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parameter. A NULL pointer shall be returned at the location pointed
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to by
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\fIresult\fP on error or if the requested entry is not found.
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.SH RETURN VALUE
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.LP
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The \fIgetpwnam\fP() function shall return a pointer to a \fBstruct
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passwd\fP with the structure as defined in \fI<pwd.h>\fP with a matching
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entry if found. A null pointer shall be returned if the requested
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entry is not found, or an error occurs. On error, \fIerrno\fP shall
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be set to indicate the error.
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.LP
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The return value may point to a static area which is overwritten by
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a subsequent call to \fIgetpwent\fP(), \fIgetpwnam\fP(), or \fIgetpwuid\fP().
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.LP
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If successful, the \fIgetpwnam_r\fP() function shall return zero;
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otherwise, an error number shall be returned to indicate the
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error.
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.SH ERRORS
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.LP
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The \fIgetpwnam\fP() and \fIgetpwnam_r\fP() functions may fail if:
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.TP 7
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.B EIO
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An I/O error has occurred.
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.TP 7
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.B EINTR
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A signal was caught during \fIgetpwnam\fP().
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.TP 7
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.B EMFILE
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{OPEN_MAX} file descriptors are currently open in the calling process.
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.TP 7
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.B ENFILE
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The maximum allowable number of files is currently open in the system.
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.sp
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.LP
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The \fIgetpwnam_r\fP() function may fail if:
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.TP 7
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.B ERANGE
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Insufficient storage was supplied via \fIbuffer\fP and \fIbufsize\fP
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to contain the data to be referenced by the resulting
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\fBpasswd\fP structure.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Getting an Entry for the Login Name
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.LP
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The following example uses the \fIgetlogin\fP() function to return
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the name of the
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user who logged in; this information is passed to the \fIgetpwnam\fP()
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function to get the user database entry for that user.
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.sp
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.RS
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.nf
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\fB#include <sys/types.h>
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#include <pwd.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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\&...
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char *lgn;
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struct passwd *pw;
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\&...
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if ((lgn = getlogin()) == NULL || (pw = getpwnam(lgn)) == NULL) {
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fprintf(stderr, "Get of user information failed.\\n"); exit(1);
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}
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\&...
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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Three names associated with the current process can be determined:
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\fIgetpwuid\fP( \fIgeteuid\fP()) returns the name associated with
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the effective user ID of the process; \fIgetlogin\fP() returns the
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name associated with the current login activity; and
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\fIgetpwuid\fP( \fIgetuid\fP()) returns the name associated with the
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real user ID of the
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process.
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.LP
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The \fIgetpwnam_r\fP() function is thread-safe and returns values
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in a user-supplied buffer instead of possibly using a static
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data area that may be overwritten by each call.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIgetpwuid\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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\fI<limits.h>\fP, \fI<pwd.h>\fP, \fI<sys/types.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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