exec.2 (2010 09)

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exec(2) exec(2)
an executable magic number (see magic (4)), it is passed to the POSIX shell as a shell script.
arg0, ..., argn are one or more pointers to null-terminated character strings. These strings constitute the
argument list available to the new program. By convention, at least arg0 must be present and point to a
string identical to path or to path ’s last component.
argv is an array of character pointers to null-terminated strings. These strings constitute the argument
list available to the new program. By convention, argv must have at least one member, and must point to
a string that is identical to path or path ’s last component. argv is terminated by a null pointer.
envp is an array of character pointers to null-terminated strings. These strings constitute the environ-
ment in which the new program runs. envp is terminated by a null pointer. For
execle() and
execve(), the C run-time start-off routine places a pointer to the environment of the calling program in
the global cell:
extern char **environ;
and it is used to pass the environment of the calling program to the new program.
Multi-threaded applications should not use the environ variable to access or modify any environment
variable while another thread is concurrently modifying any environment variable. Calling any function
which is dependent upon any environment variable is considered a use of the environ variable to access
that environment variable.
Open file descriptors remain open, except for those whose close-on-exec flag is set (see fcntl (2)). The file
offset, access mode, and status flags of open file descriptors are unchanged.
Note that normal executable files are open only briefly when they start execution. Other executable file
types can be kept open for a long time, or even indefinitely under some circumstances.
The processing of signals by the process is unchanged by
exec*(), except that signals caught by the pro-
cess are set to their default values (see signal (2)).
If the set-user-ID mode bit of the executable file pointed to by path or file is set (see chmod(2)),
exec*()
sets the effective user ID of the new process to the user ID of the executable file. Similarly, if the set-
group-ID mode bit of the executable file is set, the effective group ID of the process is set to the group ID
of the executable file. The real user ID and real group ID of the process are unchanged. Normally, the
set-user-ID and set-group-ID functions do not apply to scripts; thus, if execlp() or execvp() executes
a script, the set-user-ID and set-group-ID bits are ignored, even if they are set. This behavior can be
overridden by setting the kernel tunable secure_sid_scripts
to zero.
The saved user ID and saved group ID of the process are always set to the effective user ID and effective
group ID, respectively, of the process at the end of the
exec*(), whether or not set-user-ID or set-
group-ID is in effect.
The shared memory segments attached to the calling program are not attached to the new program (see
shmop(2)).
Text and data segment memory locks are not passed on to the new program (see plock (2)).
Profiling is disabled for the new process (see profil (2)).
The process also retains the following attributes:
• current working directory
• file creation mode mask (see umask(2))
• file locks (see fcntl (2)), except for files closed-on-execution
• file size limit (see ulimit (2))
• interval timers (see getitimer (2))
• nice value (see nice (2))
• nice value (see parent process ID)
• pending signals
• process ID
• process group ID
• real user ID
• real group ID
• process start time
• real-time priority (see rtprio (2))
• root directory (see chroot (2))
2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010