|EXECVE(2)||System Calls Manual||EXECVE(2)|
— execute a file
char *path, char *const
argv, char *const
char *path, char *const
argv, char *const
transforms the calling process into a new process. The new process is
constructed from an ordinary file, whose name is pointed to by
path, called the
file. This file is either an executable object file, or a file of
data for an interpreter. An executable object file consists of an
identifying header, followed by pages of data representing the initial
program (text) and initialized data pages. Additional pages may be specified
by the header to be initialized with zero data; see
An interpreter file begins with a line of the form:
When an interpreter file is passed to
the system instead calls
execve() with the specified
interpreter. If the optional arg is
specified, it becomes the first argument to the
interpreter, and the original path
becomes the second argument; otherwise, path becomes
the first argument. The original arguments are shifted over to become the
subsequent arguments. The zeroth argument, normally the name of the file
being executed, is left unchanged.
The argument argv is a pointer to a null-terminated array of character pointers to NUL-terminated character strings. These strings construct the argument list to be made available to the new process. At least one non-null argument must be present in the array; by custom, the first element should be the name of the executed program (for example, the last component of path).
The argument envp is also a pointer to a null-terminated array of character pointers to NUL-terminated strings. A pointer to this array is normally stored in the global variable environ. These strings pass information to the new process that is not directly an argument to the command (see environ(7)).
File descriptors open in the calling process image
remain open in the new process image, except for those for which the
close-on-exec flag is set (see
fcntl(2)). Descriptors that
remain open are unaffected by
In the case of a new setuid or setgid executable being executed, if file
descriptors 0, 1, or 2 (representing stdin, stdout, and stderr) are
currently unallocated, these descriptors will be opened to point to some
system file like /dev/null. The intent is to ensure
these descriptors are not unallocated, since many libraries make assumptions
about the use of these 3 file descriptors.
Signals set to be ignored in the calling process are set to be ignored in the new process. Signals which are set to be caught in the calling process image are set to default action in the new process image. Blocked signals remain blocked regardless of changes to the signal action. The signal stack is reset to be undefined (see sigaction(2) for more information).
If the set-user-ID mode bit of the new process image file is set (see chmod(2)), the effective user ID of the new process image is set to the owner ID of the new process image file. If the set-group-ID mode bit of the new process image file is set, the effective group ID of the new process image is set to the group ID of the new process image file. (The effective group ID is the first element of the group list.) The real user ID, real group ID and other group IDs of the new process image remain the same as the calling process image. After any set-user-ID and set-group-ID processing, the effective user ID is recorded as the saved set-user-ID, and the effective group ID is recorded as the saved set-group-ID. These values may be used in changing the effective IDs later (see setuid(2)). The set-user-ID and set-group-ID bits have no effect if the new process image file is located on a file system mounted with the nosuid flag. The process will be started without the new permissions.
The new process also inherits the following attributes from the calling process:
When a program is executed as a result of an
call, it is entered as follows:
main(int argc, char **argv, char **envp)
where argc is the number of elements in argv (the “arg count”) and argv points to the array of character pointers to the arguments themselves.
execve() function overlays the
current process image with a new process image the successful call has no
process to return to. If
execve() does return to the
calling process an error has occurred; the return value will be -1 and the
global variable errno is set to indicate the
execve() will fail and return to the
calling process if:
NAME_MAXcharacters, or an entire pathname (including the terminating NUL) exceeded
execve() function is expected to
conform to IEEE Std 1003.1-2008
function should not be used in portable applications.
The predecessor of these functions, the former
exec() system call, first appeared in
Version 1 AT&T UNIX. The
execve() function first appeared in
Version 7 AT&T UNIX.
|July 28, 2015||OpenBSD-5.8|