Sistemi operativi - Syscall exec

exec http://www.opengroup.org/onlinepubs/007908799/xsh/exec.html

The Single UNIX ® Specification, Version 2

Copyright © 1997 The Open Group

NAME

environ, execl, execv, execle, execve, execlp, execvp - execute a file

SYNOPSIS

#include <unistd.h>

extern char **environ;

int execl(const char *path, const char *arg0, ... /*, (char *)0 */);

int execv(const char *path, char *const argv[]);

int execle(const char *path,

const char *arg0, ... /*, (char *)0, char *const envp[]*/);

int execve(const char *path, char *const char *const

argv[], envp[]);

int execlp(const char *file, const char *arg0, ... /*, (char *)0 */);

int execvp(const char *file, char *const argv[]);

DESCRIPTION

The exec functions replace the current process image with a new process image. The new

image is constructed from a regular, executable file called the new process image file. There

is no return from a successful exec, because the calling process image is overlaid by the new

process image.

When a C-language program is executed as a result of this call, it is entered as a C-language

function call as follows:

int main (int argc, char *argv[]);

where argc is the argument count and argv is an array of character pointers to the arguments

themselves. In addition, the following variable:

extern char **environ;

is initialised as a pointer to an array of character pointers to the environment strings. The argv

and environ arrays are each terminated by a null pointer. The null pointer terminating the

argv array is not counted in argc.

Conforming multi-threaded applications will not use the environ variable to access or modify

any environment variable while any other thread is concurrently modifying any environment

variable. A call to any function dependent on any environment variable is considered a use of

the environ variable to access that environment variable.

The arguments specified by a program with one of the exec functions are passed on to the

new process image in the corresponding main() arguments.

The argument path points to a pathname that identifies the new process image file.

The argument file is used to construct a pathname that identifies the new process image file.

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exec http://www.opengroup.org/onlinepubs/007908799/xsh/exec.html

If the file argument contains a slash character, the file argument is used as the pathname for

this file. Otherwise, the path prefix for this file is obtained by a search of the directories

passed as the environment variable (see specification, ). If this

XBD Environment Variables

environment variable is not present, the results of the search are implementation-dependent.

execlp() and execvp() use the

If the process image file is not a valid executable object,

contents of that file as standard input to a command interpreter conforming to system(). In

this case, the command interpreter becomes the new process image.

The arguments represented by arg0, ... are pointers to null-terminated character strings. These

strings constitute the argument list available to the new process image. The list is terminated

by a null pointer. The argument arg0 should point to a filename that is associated with the

process being started by one of the exec functions.

The argument argv is an array of character pointers to null-terminated strings. The last

member of this array must be a null pointer. These strings constitute the