How to use execvp or any of the other exec's to run on only one file?-CodePudding

I want to execute execvp, or really any of them that would work for this, but only run it on the file given. To explain what I am trying to do, I am trying to run it on files that meet the other arguments given. Ex: (./a.out -s 1024 -e "ls -l") -s being if the file size is >= 1024 then show that file and then excute the command "ls -l" on that file. My code checks every file in the directory and only shows the ones that pass. I am having trouble understanding how I would just show that one file and not all the files in the directory.

if (flagArgs.e_flag) // e case
{
    char *cmd = "ls";
    char *argv[3];
    argv[0] = "ls";
    argv[1] = "-la";
    argv[2] = NULL;
    printf("DIRFILE: %s\n", dirfile);

    if (strcmp(line, "") != 0){
        if ((pid = fork()) < 0) {     /* fork a child process           */
            printf("*** ERROR: forking child process failed\n");
            exit(1);
        }
        else if (pid == 0) {          /* for the child process:         */
            if (execvp(dirfile, argv) < 0) {     /* execute the command  */
                printf("*** ERROR: exec failed\n");
                exit(1);
            }
        }
        else {                                  /* for the parent:      */
            while (wait(&status) != pid)       /* wait for completion  */
                ;
        }
    }

}

I understand that i am using execvp wrong in this code as i should be passing (cmd, argv) but I am trying to figure out how i can just run the given command on one singular file. Is there any way i can do this or is using execvp wrong?

Thanks for any help!

CodePudding user response：

Add the filename to the argv array. The first argument to execvp() should be the program to run, which is usually the same as argv[0].

if (flagArgs.e_flag) // e case
{
    char *cmd = "ls";
    char *argv[4];
    argv[0] = "ls";
    argv[1] = "-la";
    argv[2] = dirfile;
    argv[3] = NULL;
    printf("DIRFILE: %s\n", dirfile);

    if (strcmp(line, "") != 0){
        if ((pid = fork()) < 0) {     /* fork a child process           */
            printf("*** ERROR: forking child process failed\n");
            exit(1);
        }
        else if (pid == 0) {          /* for the child process:         */
            if (execvp(argv[0], argv) < 0) {     /* execute the command  */
                printf("*** ERROR: exec failed\n");
                exit(1);
            }
        }
        else {                                  /* for the parent:      */
            while (wait(&status) != pid)       /* wait for completion  */
                ;
        }
    }
}