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execle()                 Execute Child Process Using Arg List and Environment

 #include   <process.h>

 int        execle(pathname, arg0,arg1...,argn,NULL,envp);
 char       *pathname;                   Path name of file to be executed
 char       *arg0,*arg1...,*argn;        List of pointers to arguments
 char       *envp[];                     Array of pointers to environment

    execle() loads and executes a new child process.  Arguments are passed
    to the child process as a list of pointers, arg0 to argn.  The child
    process is placed in the memory currently occupied by the calling
    process. There must be sufficient memory to load and execute the child
    process.

    'pathname' specifies the file name of the child process.  If
    'pathname' has a file name extension, then only that file is searched
    for. If 'pathname' ends with a period (.), then 'pathname' without an
    extension is searched for.  If 'pathname' has no extension and does
    not end with a period, then execle() searches for 'pathname' and, if
    it is not found, appends ".EXE" and searches again.

     'arg0', 'arg1',...'argn' are passed to the child process as command
    line parameters.  A NULL pointer must follow 'argn' to terminate the
    list of arguments. 'arg0' must not be NULL, and is usually set to
    'pathname'.

    The combined length of all the strings forming the argument list
    passed to the child process must not exceed 128 bytes.  This includes
    "n" (for 0-n arguments) and space characters (required to separate the
    arguments), but does not include the null ('\0') terminating
    character.

    'envp' points to an array of pointers that in turn point to strings
    that define environment variables.  These strings usually have the
    form:  "ENVVAR=value" where "ENVVAR" is the name of the environment
    variable and "value' is the string value to set it to.  The 'envp'
    array is terminated by a NULL pointer.  If 'envp' is NULL, then the
    child process acquires the environment of the calling process.

    Returns:    If execle() is successful, it does not return to the
                calling process. (See the spawn...() routines for a
                similar function that can return to the calling process).
                If an error occurs, execle() returns -1 to the calling
                process. On error, 'errno' (defined in <stdlib.h>) is set
                to one of the following values (defined in <errno.h>):

                    E2BIG       Argument list or environment list too big.
                                (List > 128 bytes, or environment > 32k)
                    EACCES      Locking or sharing violation on file.
                                   (MS-DOS 3.0 and later)
                    EMFILE      Too many files open.
                    ENOENT      File or path not found.
                    ENOEXEC     File not executable.
                    ENOMEM      Not enough memory.

      Notes:    Any file open when an exec call is made remains open in
                the child process.  This includes 'stdin','stdout',
                'stderr', 'stdaux', and 'stdprn'.

                execle() does not preserve the translation modes of open
                files.  Use setmode() in the child process to set the
                desired translation modes.

                'environ' (defined in <stdlib.h>) points to a list of
                environment settings for the current process.

                See the spawn...() routines for similar though more
                flexible functions that can return to the calling program.

    Caution:    The file pointers to open buffered files are not always
                preserved correctly.  The information in the buffer may be
                lost.

                Signal settings are not preserved.  They are reset to the
                default in the child process.

  -------------------------------- Example ---------------------------------

    The following statements transfer execution to the child process
    "child.exe" and pass it the three arguments "child", "arg1", and
    "arg2".  The PATH environment variable is set to "C:\\TEST":

            #include <process.h>    /* for 'execle' */
            #include <stdio.h>      /* for 'printf' and 'NULL' */
            #include <stdlib.h>     /* for 'errno' */
            #include <errno.h>      /* for 'ENOENT' and 'ENOMEM' */

            char *env[] = {"PATH=C:\\TEST", NULL};

            main()
            {
                execle("child.exe", "child", "arg1", "arg2", NULL, env);
                /* only get here on an exec error */
                if (errno == ENOENT)
                    printf("child.exe not found in current directory\n");
                else if (errno == ENOMEM)
                    printf("not enough memory to execute child.exe\n");
                else
                    printf("error #%d trying to exec child.exe\n", errno);
             }