Question

My program basically runs a executable file with command line arguments.
A child process is forked and the output of the child process is taken in the file “filename”.

The problem is that the file is made and the data is written but it can only be opened by the root user.. How can make it readable to the user who invoked the program?

The code is:

    #include<stdio.h>
    #include<string.h>      //strcpy() used
    #include<malloc.h>      //malloc() used
    #include<unistd.h>      //fork() used
    #include<stdlib.h>      //exit() function used
    #include<sys/wait.h>    //waitpid() used
    #include<fcntl.h>

    int main(int argc, char **argv)
    {
char *command;
char input[256];
char **args=NULL;
char *arg;
int count=0;
char *binary;
pid_t pid;
int fdw;

printf("Enter the name of the executable(with full path)");
fgets(input,256,stdin);

command = malloc(strlen(input));
strncpy(command,input,strlen(input)-1);

binary=strtok(command," ");
args=malloc(sizeof(char*));

args[0]=malloc(strlen(binary)+1);
strcpy(args[0],binary);

while ((arg=strtok(NULL," "))!=NULL)
{
    if ( count%10 == 0) args=realloc(args,sizeof(char*)*10);
    count++;
    args[count]=malloc(strlen(arg));
    strcpy(args[count],arg);
}
args[++count]=NULL;

if ((fdw=open("filename",O_WRONLY|O_EXCL|O_CREAT|0700)) == -1)
    perror("Error making file");
close(1);
dup(fdw);

if ((pid = fork()) == -1)
{
    perror("Error forking...\n");
    exit(1);
}
if (pid == 0)   execvp(args[0],&args[0]);
else
{
    int status;
    waitpid(-1, &status, 0);
}
return 0;
}

Answer 1

Re-read the manpage for open, you are not passing the file mode argument correctly and causing the flags to be messed up in the process.