Originální popis anglicky:
execve - execute program
Návod, kniha: Linux Programmer's Manual
#include <unistd.h>
int execve(const char *filename, char *const argv
[], char *const envp[]);
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. The SIGCHLD signal (when set to SIG_IGN) may
or may not be reset to SIG_DFL.
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
/lib/ld-linux.so.1 for binaries linked with
the Linux libc version 5, or
/lib/ld-linux.so.2 for binaries linked
with the GNU libc version 2.
On success,
execve() does not return, on error -1 is returned, and
errno is set appropriately.
- E2BIG
- The argument list is too big.
- EACCES
- Search permission is denied on a component of the path
prefix of filename or the name of a script interpreter. (See also
path_resolution(2).)
- EACCES
- The file or a script interpreter is not a regular
file.
- EACCES
- Execute permission is denied for the file or a script or
ELF interpreter.
- EACCES
- The file system is mounted noexec.
- EFAULT
- filename points outside your accessible address
space.
- EINVAL
- An ELF executable had more than one PT_INTERP segment
(i.e., tried to name more than one interpreter).
- EIO
- An I/O error occurred.
- EISDIR
- An ELF interpreter was a directory.
- ELIBBAD
- An ELF interpreter was not in a recognised format.
- ELOOP
- Too many symbolic links were encountered in resolving
filename or the name of a script or ELF interpreter.
- EMFILE
- The process has the maximum number of files open.
- ENAMETOOLONG
- filename is too long.
- ENFILE
- The system limit on the total number of open files has been
reached.
- ENOENT
- The file filename or a script or ELF interpreter
does not exist, or a shared library needed for file or interpreter cannot
be found.
- 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.
- 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.
- 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.
- ETXTBSY
- Executable was open for writing by one or more
processes.
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.
SUID and SGID processes can not be
ptrace()d.
Linux ignores the SUID and SGID bits on scripts.
The result of mounting a filesystem
nosuid vary between Linux kernel
versions: some will refuse execution of SUID/SGID executables when this would
give the user powers she did not have already (and return EPERM), some will
just ignore the SUID/SGID bits and exec successfully.
A maximum line length of 127 characters is allowed for the first line in a #!
executable shell script.
With Unix V6 the argument list of an exec call was ended by 0, while the
argument list of
main was ended by -1. Thus, this argument list was not
directly usable in a further exec call. Since Unix V7 both are NULL.
chmod(2),
fork(2),
path_resolution(2),
execl(3),
environ(5),
ld.so(8)
