Section: Linux Programmer's Manual (3)
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fexecve - execute program specified via file descriptor
int fexecve(int fd, char *const argv, char *const envp);
Feature Test Macro Requirements for glibc (see
- Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
performs the same task as
with the difference that the file to be executed
is specified via a file descriptor,
rather than via a pathname.
The file descriptor
must be opened read-only
or with the
and the caller must have permission to execute the file that it refers to.
A successful call to
On error, the function does return, with a result value of -1, and
is set appropriately.
Errors are as for
with the following additions:
is not a valid file descriptor, or
is NULL, or
filesystem could not be accessed.
is implemented since glibc 2.3.2.
For an explanation of the terms used in this section, see
This function is not specified in POSIX.1-2001,
and is not widely available on other systems.
It is specified in POSIX.1-2008.
On Linux with glibc versions 2.26 and earlier,
is implemented using the
needs to be mounted and available at the time of the call.
Since glibc 2.27,
if the underlying kernel supports the
system call, then
is implemented using that system call, with the benefit that
does not need to be mounted.
The idea behind
is to allow the caller to verify (checksum) the contents of
an executable before executing it.
Simply opening the file, checksumming the contents, and then doing an
would not suffice, since, between the two steps, the filename,
or a directory prefix of the pathname, could have been exchanged
(by, for example, modifying the target of a symbolic link).
does not mitigate the problem that the
of a file could be changed between the checksumming and the call to
for that, the solution is to ensure that the permissions on the file
prevent it from being modified by malicious users.
The natural idiom when using
is to set the close-on-exec flag on
so that the file descriptor does not leak through to the program
that is executed.
This approach is natural for two reasons.
First, it prevents file descriptors being consumed unnecessarily.
(The executed program normally has no need of a file descriptor
that refers to the program itself.)
is used recursively,
employing the close-on-exec flag prevents the file descriptor exhaustion
that would result from the fact that each step in the recursion would
cause one more file descriptor to be passed to the new program.
(But see BUGS.)
refers to a script (i.e., it is an executable text file that names
a script interpreter with a first line that begins with the characters
and the close-on-exec flag has been set for
fails with the error
This error occurs because,
by the time the script interpreter is executed,
has already been closed because of the close-on-exec flag.
Thus, the close-on-exec flag can't be set on
if it refers to a script, leading to the problems described in NOTES.
This page is part of release 4.16 of the Linux
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at