"Linux Advanced Programming" (chapter eighth) process management and program development 2

Running new code in the process

The EXECX series function can run a new program in the current child process. When a process invokes any function in the series, the process's user-space resources are completely replaced by the new program.

The difference between these functions: Indicates whether the location of the new program uses a path or a file name, and if the file name searches for the program in the path described by the system's $PATH environment variable.

How to use the parameter list or use the argv[] array when using parameters

functions           &NBSP ;	using the filename	using the pathname	using the Parameter table (function appears letter L)	using argv (function appears letter V)
execl		√	√
execlp	√		Yes
execle		√	√
execv		√		√
execvp	√			√
execve		√		√

int execl (__const char *__path, __const char * __arg, ...): Executes the program pointed to by the path string, followed by a parameter list. Finally, you must pass in a null pointer .

#include <unistd.h>#include<stdio.h>#include<sys/types.h>intMainintargcChar*argv[])    {pid_t pid; if(PID = fork ()) <0) printf ("error\n"); Else if(PID = =0) {execl ("/bin/ls","ls","- L"," /Home",(Char*)0);//child Process Execution new function    }    Elseprintf ("Father ok!\n"); return 0;}

int execle (__const char * __path, __const char *__arg, ...): The last parameter must point to a new array of environment variables , the environment variable for the new execution program.

#include <unistd.h>intMainintargcChar*argv[],Char*env[]) {Execl ("/bin/ls","ls","- L"," /Home",(Char *)0 ,Env);//child Process Execution new function    return 0;}

int EXECLP (__const char * __file, __const char * __arg, ...): Finds the file in the $PATH environment variable and executes, the last argument must be null with a null pointer

#include <unistd.h>intMainintargcChar*argv[],Char*env[]) {EXECLP ("ls","ls","- L"," /Home",(Char*)0);//child Process Execution new function    return 0;}

int Execv (__const char * __path, char * __const __argv[]): The second parameter is a list of program parameters maintained by the array pointer. the last member of the array must be null.

#include <unistd.h>intMain () {Char* argv[] = {"ls","- L"," /Home",(Char*)0}; EXECV ("/bin/ls", argv);//child Process Execution new function        return 0;}

int EXECVP (__const char * file, char * __const __argv[]): Using the file name, the last member of the second argument must be null.

 #include <unistd.h>int   main () {  char  * argv[] = { " ls  , "   -L  , "   /home  , (char  *) 0  }; EXECVP (  ls  , argv); //         child process Execute new function  return  0  ;}  

int System (__const char * __command): Creates a new process and runs until the new process finishes running before the parent process continues.

#include <stdlib.h>#include<sys/wait.h>#include<stdio.h>intMainintargcChar*argv[]) {    intstatus; Status= System ("pwd"); if(!wifexited (status)) printf ("Abnormal exit\n"); Elseprintf ("The exit status is%d\n", status); return 0;}

Linux Advanced Programming (chapter eighth) process management and program development 2