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Manuál Linux
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stat: získat stav souboru

Originální popis anglicky: stat - get file status

Návod, kniha: POSIX Programmer's Manual


#include <sys/stat.h>
int stat(const char *restrict path, struct stat *restrict buf);


The stat() function shall obtain information about the named file and write it to the area pointed to by the buf argument. The path 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 stat() to fail. In particular, the system may deny the existence of the file specified by path.
If the named file is a symbolic link, the stat() 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.
The buf argument is a pointer to a stat structure, as defined in the <sys/stat.h> header, into which information is placed concerning the file.
The stat() 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 stat structure.
Unless otherwise specified, the structure members st_mode, st_ino, st_dev, st_uid, st_gid, st_atime, st_ctime, and st_mtime shall have meaningful values for all file types defined in this volume of IEEE Std 1003.1-2001. The value of the member st_nlink shall be set to the number of links to the file.


Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.


The stat() function shall fail if:
Search permission is denied for a component of the path prefix.
An error occurred while reading from the file system.
A loop exists in symbolic links encountered during resolution of the path argument.
The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.
A component of path does not name an existing file or path is an empty string.
A component of the path prefix is not a directory.
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 buf.
The stat() function may fail if:
More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.
As a result of encountering a symbolic link in resolution of the path argument, the length of the substituted pathname string exceeded {PATH_MAX}.
A value to be stored would overflow one of the members of the stat structure.
The following sections are informative.


Obtaining File Status Information

The following example shows how to obtain file status information for a file named /home/cnd/mod1. The structure variable buffer is defined for the stat structure.
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h>
struct stat buffer; int status; ... status = stat("/home/cnd/mod1", &buffer);

Getting Directory Information

The following example fragment gets status information for each entry in a directory. The call to the stat() function stores file information in the stat structure pointed to by statbuf. The lines that follow the stat() call format the fields in the stat structure for presentation to the user of the program.
#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>
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) {
/* Get entry's information. */ if (stat(dp->d_name, &statbuf) == -1) continue;
/* Print out type, permissions, and number of links. */ printf("%10.10s", sperm (statbuf.st_mode)); printf("%4d", statbuf.st_nlink);
/* 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);
/* 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);
/* Print size of file. */ printf(" %9jd", (intmax_t)statbuf.st_size);
tm = localtime(&statbuf.st_mtime);
/* Get localized date string. */ strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);
printf(" %s %s\n", datestring, dp->d_name); }




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 stat() 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 fstat() function calls even though it has a valid file descriptor open for writing.




fstat() , lstat() , readlink() , symlink() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>, <sys/types.h> 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 .
2003 IEEE/The Open Group
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