How to redirect a printf output to file?-CodePudding

I want to write the PID to a specific file. It echoes the pid in terminal so far. But how to write this PID to a file?

int main()
{
pid_t pid = getpid();
printf("%lu\n", pid);

char *filename = "/.wirebot/pid.txt";
char *home_dir = getenv("HOME");
char *filepath = malloc(strlen(home_dir)   strlen(filename)   1);
strncpy(filepath, home_dir, strlen(home_dir)   1);
strncat(filepath, filename, strlen(filename)   1);

FILE *fp;
fp = fopen(filepath, "w");
 if (fp == NULL) {
} else {
    fputs("%lu\n", pid, fp);
    fclose(fp);
    }

}

Too many arguments at fputs is the error I get.

CodePudding user response：

You should take a look at fprintf() function. Just remember to check(From you code i guess you are probably trying things with processes and then you will try it with forking), how to handle multiple processes writing to the same file.

CodePudding user response：

Here is a sample code to do that. You open a file and then use fprintf to write into it.

// C Program for the above approach  
#include<stdio.h>
int main()
{
    int i, n=2;
    char str[50];
   
    //open file sample.txt in write mode
    FILE *fptr = fopen("sample.txt", "w");
    if (fptr == NULL)
    {
        printf("Could not open file");
        return 0;
    }
   
    for (i = 0; i < n; i  )
    {
        puts("Enter a name");
        scanf("%[^\n]%*c", str);
        fprintf(fptr,"%d.%s\n", i, str);
    }
    fclose(fptr);
   
    return 0;
}