Execute a file


#include <process.h>

int execlpe( const char * file, 
             const char * arg0, 
             const char * arg1,
             const char * argn, 
             const char * envp[] );


Used to construct a pathname that identifies the new process image file. If the file argument contains a slash character, the file argument is used as the pathname for the file. Otherwise, the path prefix for this file is obtained by a search of the directories passed as the environment variable PATH.
Pointers to NULL-terminated character strings. These strings constitute the argument list available to the new process image. You must terminate the list with a NULL pointer. The arg0 argument must point to a filename that's associated with the process and cannot be NULL.
An array of character pointers to NULL-terminated strings. These strings constitute the environment for the new process image. Terminate the envp array with a NULL pointer.



Use the -l c option to qcc to link against this library. This library is usually included automatically.


Note: See execl() for further information on the exec*() family of functions.

The execlpe() function replaces the current process image with a new process image specified by file. The new image is constructed from a regular, executable file called the new process image file. No return is made because the calling process image is replaced by the new process image.

  • In order to start the new process, your process must have the PROCMGR_AID_SPAWN ability enabled. For more information, see procmgr_ability().
  • If the new child process is a shell script, the first line must start with #!, followed by the path of the program to run to interpret the script, optionally followed by one argument. The script must also be marked as executable. For more information, see The first line in the Writing Shell Scripts chapter of the QNX Neutrino User's Guide.

The execlpe() function uses the paths listed in the PATH environment variable to locate the program to be loaded, provided that the following conditions are met:

The process is started with the arguments specified in the NULL-terminated arguments arg1argn. arg0 should point to a filename associated with the program being loaded. Only arg0 is required, arg1argn are optional.

The new process's environment is specified in envp, a NULL-terminated array of NULL-terminated strings. envp cannot be NULL, but envp[0] can be a NULL pointer if no environment strings are passed.

Each pointer in envp points to a string in the form:


that is used to define an environment variable.

The environment is the collection of environment variables whose values have been defined with the export shell command, the env utility, or by the successful execution of the putenv() or setenv() functions. A program may read these values with the getenv() function.

An error is detected when the program can't be found.

If the file is on a filesystem mounted with the ST_NOSUID flag set, the effective user ID, effective group ID, saved set-user ID and saved set-group ID are unchanged for the new process. Otherwise, if the set-user ID mode bit is set, the effective user ID of the new process is set to the owner ID of file. Similarly, if the set-group ID mode bit is set, the effective group ID of the new process is set to the group ID of file. The real user ID, real group ID and supplementary group IDs of the new process remain the same as those of the calling process. The effective user ID and effective group ID of the new process are saved as the saved set-user ID and the saved set-group ID used by setuid().

If the calling process had locked any memory, the locks are released.

exec*() summary

Function Description POSIX?
execl() NULL-terminated argument list Yes
execle() NULL-terminated argument list, specify the new process's environment Yes
execlp() NULL-terminated argument list, search for the new process in PATH Yes
execlpe() NULL-terminated argument list, search for the new process in PATH, specify the new process's environment No
execv() NULL-terminated array of arguments Yes
execve() NULL-terminated array of arguments, specify the new process's environment Yes
execvp() NULL-terminated array of arguments, search for the new process in PATH Yes
execvpe() NULL-terminated array of arguments, search for the new process in PATH, specify the new process's environment No


When execlpe() is successful, it doesn't return; otherwise, it returns -1 and sets errno.


The argument list and the environment is larger than the system limit of ARG_MAX bytes.
The calling process doesn't have permission to search a directory listed in file, or it doesn't have permission to execute file, or file's filesystem was mounted with the ST_NOEXEC flag.
The arg0 argument is NULL.
Too many levels of symbolic links or prefixes.
Insufficient resources available to load the new executable image or to remap file descriptors.
The length of file or an element of the PATH environment variable exceeds PATH_MAX.
One or more components of the pathname don't exist, or the file argument points to an empty string.
There's insufficient memory available to create the new process.
A component of file isn't a directory.
The calling process doesn't have the required permission (see procmgr_ability()), or an underlying call to mmap() failed because it attempted to set PROT_EXEC for a region of memory covered by an untrusted memory-mapped file.
The text file that you're trying to execute is busy (e.g., it might be open for writing).


QNX Neutrino

Cancellation point No
Interrupt handler No
Signal handler No
Thread Yes