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EXECVE(2)                  Linux Programmer's Manual                 EXECVE(2)

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.  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.

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 or ELF
              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,
              or a shared library needed for file or interpreter cannot be
              found.

       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.

       ETXTBSY
              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.

       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.

SEE ALSO
       chmod(2), fork(2), execl(3), environ(5), ld.so(8)

Linux 2.0.30                      1997-09-03                         EXECVE(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO

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