man-pages/man3p/stat.3p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "STAT" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" stat 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
stat \- get file status
.SH SYNOPSIS
.LP
\fB#include <sys/stat.h>
.br
.sp
int stat(const char *restrict\fP \fIpath\fP\fB, struct stat *restrict\fP
\fIbuf\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
The \fIstat\fP() function shall obtain information about the named
file and write it to the area pointed to by the \fIbuf\fP
argument. The \fIpath\fP argument points to a pathname naming a file.
Read, write, or execute permission of the named file is not
required. An implementation that provides additional or alternate
file access control mechanisms may, under implementation-defined
conditions, cause \fIstat\fP() to fail. In particular, the system
may deny the existence of the file specified by \fIpath\fP.
.LP
If the named file is a symbolic link, the \fIstat\fP() function shall
continue pathname resolution using the contents of the
symbolic link, and shall return information pertaining to the resulting
file if the file exists.
.LP
The \fIbuf\fP argument is a pointer to a \fBstat\fP structure, as
defined in the \fI<sys/stat.h>\fP header, into which information is
placed concerning the file.
.LP
The \fIstat\fP() function shall update any time-related fields (as
described in the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 4.7, File Times Update), before writing
into the \fBstat\fP structure.
.LP
Unless otherwise specified, the structure members \fIst_mode\fP, \fIst_ino\fP,
\fIst_dev\fP, \fIst_uid\fP, \fIst_gid\fP,
\fIst_atime\fP, \fIst_ctime\fP, and \fIst_mtime\fP shall have meaningful
values for all file types defined in this volume of
IEEE\ Std\ 1003.1-2001. The value of the member \fIst_nlink\fP shall
be set to the number of links to the file.
.SH RETURN VALUE
.LP
Upon successful completion, 0 shall be returned. Otherwise, -1 shall
be returned and \fIerrno\fP set to indicate the error.
.SH ERRORS
.LP
The \fIstat\fP() function shall fail if:
.TP 7
.B EACCES
Search permission is denied for a component of the path prefix.
.TP 7
.B EIO
An error occurred while reading from the file system.
.TP 7
.B ELOOP
A loop exists in symbolic links encountered during resolution of the
\fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
The length of the \fIpath\fP argument exceeds {PATH_MAX} or a pathname
component is longer than {NAME_MAX}.
.TP 7
.B ENOENT
A component of \fIpath\fP does not name an existing file or \fIpath\fP
is an empty string.
.TP 7
.B ENOTDIR
A component of the path prefix is not a directory.
.TP 7
.B EOVERFLOW
The file size in bytes or the number of blocks allocated to the file
or the file serial number cannot be represented correctly
in the structure pointed to by \fIbuf\fP.
.sp
.LP
The \fIstat\fP() function may fail if:
.TP 7
.B ELOOP
More than {SYMLOOP_MAX} symbolic links were encountered during resolution
of the \fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
As a result of encountering a symbolic link in resolution of the \fIpath\fP
argument, the length of the substituted pathname
string exceeded {PATH_MAX}.
.TP 7
.B EOVERFLOW
A value to be stored would overflow one of the members of the \fBstat\fP
structure.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Obtaining File Status Information
.LP
The following example shows how to obtain file status information
for a file named \fB/home/cnd/mod1\fP. The structure variable
\fIbuffer\fP is defined for the \fBstat\fP structure.
.sp
.RS
.nf

\fB#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
.sp

struct stat buffer;
int         status;
\&...
status = stat("/home/cnd/mod1", &buffer);
\fP
.fi
.RE
.SS Getting Directory Information
.LP
The following example fragment gets status information for each entry
in a directory. The call to the \fIstat\fP() function
stores file information in the \fBstat\fP structure pointed to by
\fIstatbuf\fP. The lines that follow the \fIstat\fP() call
format the fields in the \fBstat\fP structure for presentation to
the user of the program.
.sp
.RS
.nf

\fB#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <locale.h>
#include <langinfo.h>
#include <stdio.h>
#include <stdint.h>
.sp

struct dirent  *dp;
struct stat     statbuf;
struct passwd  *pwd;
struct group   *grp;
struct tm      *tm;
char            datestring[256];
\&...
/* Loop through directory entries. */
while ((dp = readdir(dir)) != NULL) {
.sp

    /* Get entry's information. */
    if (stat(dp->d_name, &statbuf) == -1)
        continue;
.sp

    /* Print out type, permissions, and number of links. */
    printf("%10.10s", sperm (statbuf.st_mode));
    printf("%4d", statbuf.st_nlink);
.sp

    /* Print out owner's name if it is found using getpwuid(). */
    if ((pwd = getpwuid(statbuf.st_uid)) != NULL)
        printf(" %-8.8s", pwd->pw_name);
    else
        printf(" %-8d", statbuf.st_uid);
.sp

    /* Print out group name if it is found using getgrgid(). */
    if ((grp = getgrgid(statbuf.st_gid)) != NULL)
        printf(" %-8.8s", grp->gr_name);
    else
        printf(" %-8d", statbuf.st_gid);
.sp

    /* Print size of file. */
    printf(" %9jd", (intmax_t)statbuf.st_size);
.sp

    tm = localtime(&statbuf.st_mtime);
.sp

    /* Get localized date string. */
    strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);
.sp

    printf(" %s %s\\n", datestring, dp->d_name);
}
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
The intent of the paragraph describing "additional or alternate file
access control mechanisms" is to allow a secure
implementation where a process with a label that does not dominate
the file's label cannot perform a \fIstat\fP() function. This
is not related to read permission; a process with a label that dominates
the file's label does not need read permission. An
implementation that supports write-up operations could fail \fIfstat\fP()
function calls
even though it has a valid file descriptor open for writing.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIfstat\fP(), \fIlstat\fP(), \fIreadlink\fP(), \fIsymlink\fP(),
the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, \fI<sys/stat.h>\fP, \fI<sys/types.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .