LINUX study note 11-process control programming

1. obtain the ID of the current process: pid_tgetpid (void). after adding this function to the program, you can obtain the idnumber of the process: printf (pid % d, getpid () when running the program ()); output in integer form a) # include & lt; unistd. h & gt; 2. obtain the parent process ID: pid_tgetppid (void... 1. obtain the ID of the current process: pid_t getpid (void). after adding this function to the program, you can get the ID of the current process: printf ("pid = % d ", getpid (); output in integer form
 
A) # include
 
2. get the parent process ID: pid_t getppid (void)
 
A) # include
 
3. create a sub-process: pid_t fork (void)
 
A) program: the created sub-process runs the code below the fork function in the parent process, shares the code segment, and copies the data segment again.
 
B) # include
 
C) role:
 
D) return value: a value is returned in both the parent and child processes.
 
1. ID: in the parent process, fork returns the ID of the child process.
 
2. negative value: an error occurs,
 
3. 0: In a sub-process, fork returns 0, which does not mean that the ID is 0.
 
4. create a sub-process: pid_t vfork (void)
 
A) # include
 
B) differences:
 
1. shared data segment
 
2. the child process runs first, and the parent process runs later. fork is not sure
 
5. replacement process: exec function family
 
A) role: the process number remains unchanged, but the new program is started to replace the original program.
 
B) Int execl (const char * path, const char * arg1 ,..., NULL)
 
1. Cxecl ("/etc/ls", "ls", "-al", "/etc/passwd", NULL)
 
2. Path: name of the program to be executed, including the complete Path
 
3. # include
 
4. Arg1-argn: the command line parameter required by the program to be executed. The 1st parameter is the program name and ends with a null pointer.
 
C) Int execlp (const char * path, const char * arg1 ,..., NULL)
 
1. Cxeclp ("ls", "ls", "-al", "/etc/passwd", NULL)
 
2. # include
 
3. Path: the name of the program to be executed, but it does not contain the complete PATH. find it from the Path command of LINUX.
 
D) Int execv (const char * path, const char * argv [], NULL)
 
1. Path: name of the program to be executed, including the complete Path
 
2. argv []: string array
 
3. # include
 
E) int system (const char * string)
 
1. example: system ("ls-al/etc/passwd ")
 
2. # include
 
F) function: call fork to generate a sub-process. The sub-process calls/bin/sh-c string to execute the command represented by the string parameter. It is equivalent to using shell to parse commands
 
6. process wait: pid_t wait (int * status)
 
A) Pid_t wait (NULL );
 
B) # include
 
C) # include
 
D) function: blocks the process until a sub-process exits.
 
E) return value: Process Number of the sub-process to exit
 
F) Status: return the process end Status value. If NULL is not required