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.\" Copyright (c) 2014 Google, Inc.
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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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.\" %%%LICENSE_END
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.\"
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2015-01-09 14:11:42 +00:00
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.TH EXECVEAT 2 2015-01-09 "Linux" "Linux Programmer's Manual"
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.SH NAME
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execveat \- execute program relative to a directory file descriptor
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.SH SYNOPSIS
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.B #include <unistd.h>
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.sp
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.BI "int execveat(int " dirfd ", const char *" pathname ","
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.br
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.BI " char *const " argv "[], char *const " envp "[],"
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.br
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.BI " int " flags );
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.SH DESCRIPTION
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.\" commit 51f39a1f0cea1cacf8c787f652f26dfee9611874
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The
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.BR execveat ()
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system call executes the program referred to by the combination of
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.I dirfd
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and
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.IR pathname .
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It operates in exactly the same way as
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.BR execve (2),
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except for the differences described in this manual page.
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If the pathname given in
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.I pathname
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is relative, then it is interpreted relative to the directory
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referred to by the file descriptor
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.I dirfd
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(rather than relative to the current working directory of
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the calling process, as is done by
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.BR execve (2)
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for a relative pathname).
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If
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.I pathname
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is relative and
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.I dirfd
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is the special value
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.BR AT_FDCWD ,
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then
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.I pathname
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is interpreted relative to the current working
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directory of the calling process (like
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.BR execve (2)).
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If
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.I pathname
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is absolute, then
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.I dirfd
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is ignored.
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If
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.I pathname
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is an empty string and the
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.BR AT_EMPTY_PATH
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flag is specified, then the file descriptor
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.I dirfd
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specifies the file to be executed (i.e.,
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.IR dirfd
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refers to an executable file, rather than a directory).
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The
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.I flags
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argument is a bit mask that can include zero or more of the following flags:
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.TP
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.BR AT_EMPTY_PATH
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If
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.I pathname
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is an empty string, operate on the file referred to by
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.IR dirfd
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(which may have been obtained using the
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.BR open (2)
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.B O_PATH
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flag).
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.TP
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.B AT_SYMLINK_NOFOLLOW
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If the file identified by
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.I dirfd
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and a non-NULL
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.I pathname
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is a symbolic link, then the call fails with the error
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.BR EINVAL .
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.SH "RETURN VALUE"
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On success,
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.BR execveat ()
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does not return.
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On error, \-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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The same errors that occur for
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.BR execve (2)
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can also occur for
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.BR execveat ().
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The following additional errors can occur for
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.BR execveat ():
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.TP
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.B EBADF
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.I dirfd
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is not a valid file descriptor.
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.TP
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.B EINVAL
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Invalid flag specified in
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.IR flags .
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.TP
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.B ENOENT
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The program identified by
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.I dirfd
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and
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.I pathname
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requires the use of an interpreter program
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(such as a script starting with "#!"), but the file descriptor
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.I dirfd
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was opened with the
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.B O_CLOEXEC
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flag, with the result that
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the program file is inaccessible to the launched interpreter.
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.TP
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.B ENOTDIR
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.I pathname
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is relative and
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.I dirfd
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is a file descriptor referring to a file other than a directory.
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.SH VERSIONS
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.BR execveat ()
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was added to Linux in kernel 3.19.
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GNU C library support is pending.
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.\" FIXME . check for glibc support in a future release
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.SH NOTES
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In addition to the reasons explained in
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.BR openat (2),
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the
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.BR execveat ()
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system call is also needed to allow
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.BR fexecve (3)
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to be implemented on systems that do not have the
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.I /proc
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filesystem mounted.
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.SH SEE ALSO
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.BR execve (2),
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.BR openat (2),
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.BR fexecve (3)
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