mirror of https://github.com/mkerrisk/man-pages
112 lines
3.3 KiB
Groff
112 lines
3.3 KiB
Groff
.\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH EUIDACCESS 3 2013-09-25 "" "Linux Programmer's Manual"
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.SH NAME
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euidaccess, eaccess \- check effective user's permissions for a file
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.SH SYNOPSIS
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.nf
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.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
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.B #include <unistd.h>
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.sp
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.BI "int euidaccess(const char *" pathname ", int " mode );
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.BI "int eaccess(const char *" pathname ", int " mode );
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.fi
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.SH DESCRIPTION
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Like
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.BR access (2),
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.BR euidaccess ()
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checks permissions and existence of the file identified by its argument
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.IR pathname .
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However, whereas
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.BR access (2),
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performs checks using the real user and group identifiers of the process,
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.BR euidaccess ()
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uses the effective identifiers.
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.I mode
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is a mask consisting of one or more of
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.BR R_OK ", " W_OK ", " X_OK ", and " F_OK ,
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with the same meanings as for
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.BR access (2).
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.BR eaccess ()
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is a synonym for
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.BR euidaccess (),
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provided for compatibility with some other systems.
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.SH RETURN VALUE
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On success (all requested permissions granted), zero is returned.
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On error (at least one bit in
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.I mode
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asked for a permission that is denied, or some other error occurred),
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\-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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As for
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.BR access (2).
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.SH VERSIONS
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The
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.BR eaccess ()
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function was added to glibc in version 2.4.
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.SH ATTRIBUTES
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.SS Multithreading (see pthreads(7))
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The
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.BR euidaccess ()
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and
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.BR eaccess ()
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functions are thread-safe.
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.SH CONFORMING TO
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These functions are nonstandard.
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Some other systems have an
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.\" e.g., FreeBSD 6.1.
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.BR eaccess ()
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function.
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.SH NOTES
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.IR Warning :
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Using this function to check a process's permissions on a file before
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performing some operation based on that information leads to race conditions:
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the file permissions may change between the two steps.
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Generally, it is safer just to attempt the desired operation and handle
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any permission error that occurs.
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This function always dereferences symbolic links.
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If you need to check the permissions on a symbolic link, use
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.BR faccessat (2)
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with the flags
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.BR AT_EACCESS
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and
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.BR AT_SYMLINK_NOFOLLOW .
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.SH SEE ALSO
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.BR access (2),
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.BR chmod (2),
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.BR chown (2),
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.BR faccessat (2),
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.BR open (2),
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.BR setgid (2),
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.BR setuid (2),
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.BR stat (2),
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.BR credentials (7),
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.BR path_resolution (7)
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