EXECVE
Section: Linux Programmer's Manual (2)
Updated: 3 September 1997
NAME
execve - execute program
SYNOPSIS
#include <unistd.h>
int execve (const char *filename, char *const argv
[], char *const envp[]);
DESCRIPTION
execve() executes the program pointed to by filename.
filename must be either a binary executable, or a script
starting with a line of the form "#! interpreter [arg]".
In the latter case, the interpreter must be a valid pathname for an
executable which is not itself a script, which will be invoked as
interpreter [arg] filename.
argv is an array of argument strings passed to the new program.
envp is an array of strings, conventionally of the form
key=value, which are passed as environment to the new
program. Both, argv and envp must be terminated by a null
pointer. The argument vector and environment can be accessed by the
called program's main function, when it is defined as int main(int
argc, char *argv[], char *envp[]).
execve() does not return on success, and the text, data, bss, and
stack of the calling process are overwritten by that of the program
loaded. The program invoked inherits the calling process's PID, and any
open file descriptors that are not set to close on exec. Signals pending
on the calling process are cleared. Any signals set to be caught by
the calling process are reset to their default behaviour.
If the current program is being ptraced, a SIGTRAP is sent to it
after a successful execve().
If the set-uid bit is set on the program file pointed to by
filename the effective user ID of the calling process is changed
to that of the owner of the program file. Similarly, when the set-gid
bit of the program file is set the effective group ID of the calling
process is set to the group of the program file.
If the executable is an a.out dynamically-linked binary executable containing
shared-library stubs, the Linux dynamic linker
ld.so(8)
is called at the start of execution to bring needed shared libraries into core
and link the executable with them.
If the executable is a dynamically-linked ELF executable, the
interpreter named in the PT_INTERP segment is used to load the needed
shared libraries. This interpreter is typically
/.li/ld-linux.so.1 for binaries linked with the Linux libc
version 5, or /.li/ld-linux.so.2 for binaries linked with the
GNU libc version 2.
RETURN VALUE
On success, execve() does not return, on error -1 is returned, and
errno
is set appropriately.
ERRORS
- EACCES
-
The file or a script interpreter is not a regular file.
- EACCES
-
Execute permission is denied for the file or a script interpreter.
- EACCES
-
The file system is mounted
noexec.
- EPERM
-
The file system is mounted
nosuid,
the user is not the superuser, and the file has an SUID or SGID bit set.
- EPERM
-
The process is being traced, the user is not the superuser and the
file has an SUID or SGID bit set.
- E2BIG
-
The argument list is too big.
- ENOEXEC
-
An executable is not in a recognised format, is for the wrong
architecture, or has some other format error that means it cannot be
executed.
- EFAULT
-
filename
points outside your accessible address space.
- ENAMETOOLONG
-
filename
is too long.
- ENOENT
-
The file
filename
or a script or ELF interpreter does not exist.
- ENOMEM
-
Insufficient kernel memory was available.
- ENOTDIR
-
A component of the path prefix of
filename
or a script or ELF interpreter is not a directory.
- EACCES
-
Search permission is denied on a component of the path prefix of
filename
or the name of a script interpreter.
- ELOOP
-
Too many symbolic links were encountered in resolving
filename
or the name of a script or ELF interpreter.
- ETXTBUSY
-
Executable was open for writing by one or more processes.
- EIO
-
An I/O error occurred.
- ENFILE
-
The limit on the total number of files open on the system has been reached.
- EMFILE
-
The process has the maximum number of files open.
- EINVAL
-
An ELF executable had more than one PT_INTERP segment (i.e., tried to
name more than one interpreter).
- EISDIR
-
An ELF interpreter was a directory.
- ELIBBAD
-
An ELF interpreter was not in a recognised format.
CONFORMING TO
SVr4, SVID, X/OPEN, BSD 4.3. POSIX does not document the #! behavior
but is otherwise compatible. SVr4 documents additional error
conditions EAGAIN, EINTR, ELIBACC, ENOLINK, EMULTIHOP; POSIX does not
document ETXTBSY, EPERM, EFAULT, ELOOP, EIO, ENFILE, EMFILE, EINVAL,
EISDIR or ELIBBAD error conditions.
NOTES
SUID and SGID processes can not be ptrace()d SUID or SGID.
A maximum line length of 127 characters is allowed for the first line in
a #! executable shell script.
Linux ignores the SUID and SGID bits on scripts.
SEE ALSO
chmod(2),
fork(2),
execl(3),
environ(5),
ld.so(8)