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Diffstat (limited to 'man2/readlink.2')
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diff --git a/man2/readlink.2 b/man2/readlink.2 deleted file mode 100644 index c476091..0000000 --- a/man2/readlink.2 +++ /dev/null @@ -1,331 +0,0 @@ -.\" Copyright (c) 1983, 1991 The Regents of the University of California. -.\" And Copyright (C) 2011 Guillem Jover <guillem@hadrons.org> -.\" And Copyright (C) 2006, 2014 Michael Kerrisk -.\" All rights reserved. -.\" -.\" SPDX-License-Identifier: BSD-4-Clause-UC -.\" -.\" @(#)readlink.2 6.8 (Berkeley) 3/10/91 -.\" -.\" Modified Sat Jul 24 00:10:21 1993 by Rik Faith (faith@cs.unc.edu) -.\" Modified Tue Jul 9 23:55:17 1996 by aeb -.\" Modified Fri Jan 24 00:26:00 1997 by aeb -.\" 2011-09-20, Guillem Jover <guillem@hadrons.org>: -.\" Added text on dynamically allocating buffer + example program -.\" -.TH readlink 2 2023-11-01 "Linux man-pages 6.7" -.SH NAME -readlink, readlinkat \- read value of a symbolic link -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <unistd.h> -.P -.BI "ssize_t readlink(const char *restrict " pathname ", char *restrict " buf , -.BI " size_t " bufsiz ); -.P -.BR "#include <fcntl.h> " "/* Definition of " AT_* " constants */" -.B #include <unistd.h> -.P -.BI "ssize_t readlinkat(int " dirfd ", const char *restrict " pathname , -.BI " char *restrict " buf ", size_t " bufsiz ); -.P -.fi -.RS -4 -Feature Test Macro Requirements for glibc (see -.BR feature_test_macros (7)): -.RE -.P -.BR readlink (): -.nf - _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L -.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED - || /* glibc <= 2.19: */ _BSD_SOURCE -.fi -.P -.BR readlinkat (): -.nf - Since glibc 2.10: - _POSIX_C_SOURCE >= 200809L - Before glibc 2.10: - _ATFILE_SOURCE -.fi -.SH DESCRIPTION -.BR readlink () -places the contents of the symbolic link -.I pathname -in the buffer -.IR buf , -which has size -.IR bufsiz . -.BR readlink () -does not append a terminating null byte to -.IR buf . -It will (silently) truncate the contents (to a length of -.I bufsiz -characters), in case the buffer is too small to hold all of the contents. -.SS readlinkat() -The -.BR readlinkat () -system call operates in exactly the same way as -.BR readlink (), -except for the differences described here. -.P -If the pathname given in -.I pathname -is relative, then it is interpreted relative to the directory -referred to by the file descriptor -.I dirfd -(rather than relative to the current working directory of -the calling process, as is done by -.BR readlink () -for a relative pathname). -.P -If -.I pathname -is relative and -.I dirfd -is the special value -.BR AT_FDCWD , -then -.I pathname -is interpreted relative to the current working -directory of the calling process (like -.BR readlink ()). -.P -If -.I pathname -is absolute, then -.I dirfd -is ignored. -.P -Since Linux 2.6.39, -.\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d -.I pathname -can be an empty string, -in which case the call operates on the symbolic link referred to by -.I dirfd -(which should have been obtained using -.BR open (2) -with the -.B O_PATH -and -.B O_NOFOLLOW -flags). -.P -See -.BR openat (2) -for an explanation of the need for -.BR readlinkat (). -.SH RETURN VALUE -On success, these calls return the number of bytes placed in -.IR buf . -(If the returned value equals -.IR bufsiz , -then truncation may have occurred.) -On error, \-1 is returned and -.I errno -is set to indicate the error. -.SH ERRORS -.TP -.B EACCES -Search permission is denied for a component of the path prefix. -(See also -.BR path_resolution (7).) -.TP -.B EBADF -.RB ( readlinkat ()) -.I pathname -is relative but -.I dirfd -is neither -.B AT_FDCWD -nor a valid file descriptor. -.TP -.B EFAULT -.I buf -extends outside the process's allocated address space. -.TP -.B EINVAL -.I bufsiz -is not positive. -.\" At the glibc level, bufsiz is unsigned, so this error can only occur -.\" if bufsiz==0. However, the in the kernel syscall, bufsiz is signed, -.\" and this error can also occur if bufsiz < 0. -.\" See: http://thread.gmane.org/gmane.linux.man/380 -.\" Subject: [patch 0/3] [RFC] kernel/glibc mismatch of "readlink" syscall? -.TP -.B EINVAL -The named file (i.e., the final filename component of -.IR pathname ) -is not a symbolic link. -.TP -.B EIO -An I/O error occurred while reading from the filesystem. -.TP -.B ELOOP -Too many symbolic links were encountered in translating the pathname. -.TP -.B ENAMETOOLONG -A pathname, or a component of a pathname, was too long. -.TP -.B ENOENT -The named file does not exist. -.TP -.B ENOMEM -Insufficient kernel memory was available. -.TP -.B ENOTDIR -A component of the path prefix is not a directory. -.TP -.B ENOTDIR -.RB ( readlinkat ()) -.I pathname -is relative and -.I dirfd -is a file descriptor referring to a file other than a directory. -.SH STANDARDS -POSIX.1-2008. -.SH HISTORY -.TP -.BR readlink () -4.4BSD -(first appeared in 4.2BSD), -POSIX.1-2001, POSIX.1-2008. -.TP -.BR readlinkat () -POSIX.1-2008. -Linux 2.6.16, -glibc 2.4. -.P -Up to and including glibc 2.4, the return type of -.BR readlink () -was declared as -.IR int . -Nowadays, the return type is declared as -.IR ssize_t , -as (newly) required in POSIX.1-2001. -.SS glibc -On older kernels where -.BR readlinkat () -is unavailable, the glibc wrapper function falls back to the use of -.BR readlink (). -When -.I pathname -is a relative pathname, -glibc constructs a pathname based on the symbolic link in -.I /proc/self/fd -that corresponds to the -.I dirfd -argument. -.SH NOTES -Using a statically sized buffer might not provide enough room for the -symbolic link contents. -The required size for the buffer can be obtained from the -.I stat.st_size -value returned by a call to -.BR lstat (2) -on the link. -However, the number of bytes written by -.BR readlink () -and -.BR readlinkat () -should be checked to make sure that the size of the -symbolic link did not increase between the calls. -Dynamically allocating the buffer for -.BR readlink () -and -.BR readlinkat () -also addresses a common portability problem when using -.B PATH_MAX -for the buffer size, -as this constant is not guaranteed to be defined per POSIX -if the system does not have such limit. -.SH EXAMPLES -The following program allocates the buffer needed by -.BR readlink () -dynamically from the information provided by -.BR lstat (2), -falling back to a buffer of size -.B PATH_MAX -in cases where -.BR lstat (2) -reports a size of zero. -.P -.\" SRC BEGIN (readlink.c) -.EX -#include <limits.h> -#include <stdio.h> -#include <stdlib.h> -#include <sys/stat.h> -#include <unistd.h> -\& -int -main(int argc, char *argv[]) -{ - char *buf; - ssize_t nbytes, bufsiz; - struct stat sb; -\& - if (argc != 2) { - fprintf(stderr, "Usage: %s <pathname>\en", argv[0]); - exit(EXIT_FAILURE); - } -\& - if (lstat(argv[1], &sb) == \-1) { - perror("lstat"); - exit(EXIT_FAILURE); - } -\& - /* Add one to the link size, so that we can determine whether - the buffer returned by readlink() was truncated. */ -\& - bufsiz = sb.st_size + 1; -\& - /* Some magic symlinks under (for example) /proc and /sys - report \[aq]st_size\[aq] as zero. In that case, take PATH_MAX as - a "good enough" estimate. */ -\& - if (sb.st_size == 0) - bufsiz = PATH_MAX; -\& - buf = malloc(bufsiz); - if (buf == NULL) { - perror("malloc"); - exit(EXIT_FAILURE); - } -\& - nbytes = readlink(argv[1], buf, bufsiz); - if (nbytes == \-1) { - perror("readlink"); - exit(EXIT_FAILURE); - } -\& - /* Print only \[aq]nbytes\[aq] of \[aq]buf\[aq], as it doesn't contain a terminating - null byte (\[aq]\e0\[aq]). */ - printf("\[aq]%s\[aq] points to \[aq]%.*s\[aq]\en", argv[1], (int) nbytes, buf); -\& - /* If the return value was equal to the buffer size, then - the link target was larger than expected (perhaps because the - target was changed between the call to lstat() and the call to - readlink()). Warn the user that the returned target may have - been truncated. */ -\& - if (nbytes == bufsiz) - printf("(Returned buffer may have been truncated)\en"); -\& - free(buf); - exit(EXIT_SUCCESS); -} -.EE -.\" SRC END -.SH SEE ALSO -.BR readlink (1), -.BR lstat (2), -.BR stat (2), -.BR symlink (2), -.BR realpath (3), -.BR path_resolution (7), -.BR symlink (7) |