第十二周

第八章代码

1、2

#include <stdio.h>
#include <unistd.h>

int main()
{
    char    *arglist[3];

    arglist[0] = "ls";
    arglist[1] = "-l";
    arglist[2] = 0 ;//NULL
    printf("* * * About to exec ls -l ");
    execvp( "ls" , arglist );
    printf("* * * ls is done. bye");

    return 0;
}

3

#include <stdio.h>
#include <unistd.h>

int main()
{
    char    *arglist[3];
    char*myenv[3];
    myenv[0] = "PATH=:/bin:";
    myenv[1] = NULL;

    arglist[0] = "ls";
    arglist[1] = "-l";
    arglist[2] = 0 ;
    printf("* * * About to exec ls -l ");

    execlp("ls", "ls", "-l", NULL);
    printf("* * * ls is done. bye ");
}

4

#include    <stdio.h>
#include<sys/types.h>
#include<unistd.h>
int main()
{
    int ret_from_fork, mypid;
    mypid = getpid();             
    printf("Before: my pid is %d ", mypid);
    ret_from_fork = fork();
    sleep(1);
    printf("After: my pid is %d, fork() said %d ",
            getpid(), ret_from_fork);

    return 0;
}

5

#include <stdio.h>
#include <unistd.h>

int main()
{
    printf("before:my pid is %d ", getpid() );
    fork();
    fork();
    printf("aftre:my pid is %d ", getpid() );

    return 0;
}

6

#include    <stdio.h>
#include <stdlib.h>
#include    <unistd.h>

int main()
{
    int fork_rv; printf("Before: my pid is %d ", getpid());

    fork_rv = fork();       /* create new process   */

    if ( fork_rv == -1 )        /* check for error  */
        perror("fork");
    else if ( fork_rv == 0 ){
        printf("I am the child.  my pid=%d ", getpid());
   
        exit(0);
    }
    else{
        printf("I am the parent. my child is %d ", fork_rv);
        exit(0);
    }

    return 0;
}

7

#include    <stdio.h>
#include <stdlib.h>
#include    <unistd.h>

int main()
{
    int fork_rv; printf("Before: my pid is %d ", getpid());

    fork_rv = fork();       /* create new process   */

    if ( fork_rv == -1 )        /* check for error  */
        perror("fork");

    else if ( fork_rv == 0 ){
        printf("I am the child.  my pid=%d ", getpid());
        printf("parent pid= %d, my pid=%d ", getppid(), getpid());
        exit(0);
    }

    else{
        printf("I am the parent. my child is %d ", fork_rv);
        sleep(10);
        exit(0);
    }

    return 0;
}

8

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int  gi=0;
int main()
{
    int li=0;
    static int si=0;
    int i=0;

    pid_t pid = fork();
    if(pid == -1){
        exit(-1);
    }
    else if(pid == 0){
        for(i=0; i<5; i++){ printf("child li:%d ", li++); sleep(1);
            printf("child gi:%d ", gi++);
            printf("child si:%d ", si++);
        }
        exit(0);
       
    }
    else{
        for(i=0; i<5; i++){
            printf("parent li:%d ", li++);
            printf("parent gi:%d ", gi++);
            sleep(1);
            printf("parent si:%d ", si++);
        }
    exit(0);   
   
    }
    return 0;
}

9

#include    <stdio.h>
#include <stdlib.h>
#include    <string.h>
#include    <unistd.h>

#define MAXARGS     20             
#define ARGLEN      100            

int execute( char *arglist[] )
{
    execvp(arglist[0], arglist);       
    perror("execvp failed");
    exit(1);
}

char * makestring( char *buf )
{
    char    *cp;

    buf[strlen(buf)-1] = '';     
    cp = malloc( strlen(buf)+1 );      
    if ( cp == NULL ){         
        fprintf(stderr,"no memory ");
        exit(1);
    }
    strcpy(cp, buf);       
    return cp;         
}

int main()
{
    char    *arglist[MAXARGS+1];       
    int     numargs;           
    char    argbuf[ARGLEN];        

    numargs = 0;
    while ( numargs < MAXARGS )
    {                  
        printf("Arg[%d]? ", numargs);
        if ( fgets(argbuf, ARGLEN, stdin) && *argbuf != ' ' )
            arglist[numargs++] = makestring(argbuf);
        else
        {
            if ( numargs > 0 ){    
                arglist[numargs]=NULL; 
                execute( arglist );
                numargs = 0;       
            }
        }
    }
    return 0;
}

10

#include    <stdio.h>
#include <stdlib.h>
#include    <string.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>
#include    <signal.h>

#define MAXARGS     20             
#define ARGLEN      100            

char *makestring( char *buf )
{
    char    *cp;

    buf[strlen(buf)-1] = '';     
    cp = malloc( strlen(buf)+1 );      
    if ( cp == NULL ){         
        fprintf(stderr,"no memory ");
        exit(1);
    }
    strcpy(cp, buf);       
    return cp;         
}

void execute( char *arglist[] )
{
    int pid,exitstatus;            

    pid = fork();                  
    switch( pid ){
        case -1:   
            perror("fork failed");
            exit(1);
        case 0:
            execvp(arglist[0], arglist);       
            perror("execvp failed");
            exit(1);
        default:
            while( wait(&exitstatus) != pid )
                ;
            printf("child exited with status %d,%d ",
                    exitstatus>>8, exitstatus&0377);
    }
}

int main()
{
    char    *arglist[MAXARGS+1];       
    int     numargs;           
    char    argbuf[ARGLEN];        

    numargs = 0;
    while ( numargs < MAXARGS )
    {                  
        printf("Arg[%d]? ", numargs);
        if ( fgets(argbuf, ARGLEN, stdin) && *argbuf != ' ' )
            arglist[numargs++] = makestring(argbuf);
        else
        {
            if ( numargs > 0 ){    
                arglist[numargs]=NULL; 
                execute( arglist );
                numargs = 0;       
            }
        }
    }
    return 0;
}

test

1

#include <stdio.h>
#include <stdlib.h>
int main()
{
    printf("hello");
    fflush(stdout);
    while(1);
}

2

#include <stdio.h>
int main()
{
    printf("hello ");
    while(1);
}

3

#include <stdio.h>

int main()
{
    fprintf(stdout, "1234", 5);
    fprintf(stderr, "abcd", 4);
}

4

#include <stdio.h>
#include <unistd.h>

#include <sys/types.h>

int main()
{
    printf("my pid: %d ", getpid());
    printf("my parent's pid: %d ", getppid());
    return 0;
}

5

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char **pp;
    pp[0] = malloc(20);

    return 0;
}

6

#include    <stdlib.h>

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

    system(argv[1]); system(argv[2]);
    return EXIT_SUCCESS;
}               /* ----------  end of function main  ---------- */

7

#include    <stdio.h>
#include <stdlib.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>

#define DELAY   4

void child_code(int delay)
{
    printf("child %d here. will sleep for %d seconds ", getpid(), delay);
    sleep(delay);
    printf("child done. about to exit ");
    exit(17);
}

void parent_code(int childpid)
{
    int wait_rv=0;      /* return value from wait() */
    wait_rv = wait(NULL);
    printf("done waiting for %d. Wait returned: %d ",
            childpid, wait_rv);
}
int main()
{
    int  newpid;
    printf("before: mypid is %d ", getpid());
    if ( (newpid = fork()) == -1 )
        perror("fork");
    else if ( newpid == 0 )
        child_code(DELAY);
    else
        parent_code(newpid);

    return 0;
}

#include    <stdio.h>
#include <stdlib.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>

#define DELAY   10

void child_code(int delay)
{
    printf("child %d here. will sleep for %d seconds ", getpid(), delay);
    sleep(delay);
    printf("child done. about to exit ");
    exit(27);
}

void parent_code(int childpid)
{
    int wait_rv;   
    int child_status;
    int high_8, low_7, bit_7;

    wait_rv = wait(&child_status);
    printf("done waiting for %d. Wait returned: %d ", childpid, wait_rv);

    high_8 = child_status >> 8;     /* 1111 1111 0000 0000 */
    low_7  = child_status & 0x7F;   /* 0000 0000 0111 1111 */
    bit_7  = child_status & 0x80;   /* 0000 0000 1000 0000 */
    printf("status: exit=%d, sig=%d, core=%d ", high_8, low_7, bit_7);
}

int main()
{
    int  newpid;

    printf("before: mypid is %d ", getpid());

    if ( (newpid = fork()) == -1 )
        perror("fork");
    else if ( newpid == 0 )
        child_code(DELAY);
    else
        parent_code(newpid);
}