AT&T UNIX™PC Unix System V Users Manual - tenox

EXEC (2) EXEC (2)
NAME execl, execv, execle, execve, execlp, execvp - execute a file
SYNOPSIS
int execl (path, argO, argl, ••• , argo, 0)
char •path, •argO, •argl, ••• , •argo;
int execv (path, argv)
char *path, •argv[ ];
int execle (path, argO, argl, ••• , argo, 0, envp)
char •path, •argO, •argl, ••• , •argo, •envp[ ];
int execve (path, argv, envp)
char •path, •argv[ ], •envp[ ];
int execlp (file, argO, argl, ••• , argo, 0)
char •file, •argO, •argl, ••• , •argo;
int execvp (file, argv)
char •file, •argv[ ];
DESCRIPTION
Exec in all its forms transforms the calling process into a new process.
The new process is constructed from an ordinary, executable
file called the new process file . This file consists of a header (see
a. out( 4)), a text segment, and a data segment. The data segment
contains an initialized portion and an uninitialized portion (bss).
There can be no return from a successful exec because the calling
process is overlaid by the new process.
When a C program is executed, it is called as follows:
main (argc, argv, envp)
int argc;
char ••argv, ••envp;
where argc is the argument count and argv is an array of character
pointers to the arguments themselves. As indicated, argc is
conventionally at least one and the first member of the array
points to a string containing the name of the file.
Path points to a path name that identifies the new process file.
File points to the new process file. The path prefix for this file is
obtained by a search of the directories passed as the environment
line "PATH =" (see environ(5)). The environment is supplied by
the shell (see sh(l)).
ArgO, arg1 , ... , argn are pointers to null-terminated character
strings. These strings constitute the argument list available to the
new process. By convention, at least argO must be present and
point to a string that is the same as path (or its last component).
Argv is an array of character pointers to null-terminated strings.
These strings constitute the argument list available to the new
process. By convention, argv must have at least one member, and
it must point to a string that is the same as path (or its last component).
Argv is terminated by a null pointer.
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