CODEWITHSUNDEEP
clinuxgccscanf
techfun
techfun

Reputation: 953

fscanf format string while parsing file

I am new in Linux. I am developing a C application. I need uid of several processes. What I am trying to do is parsing /proc/pid/status file to get Uid of processes.

Name:    init
State:    S (sleeping)
Tgid:    1
Pid:    1
PPid:    0
TracerPid:    0
Uid: 0    0     0     0   0

To parse this file I am thinking of using fscanf function.

Here I want to write some generic code, which works for different lengths of process. But I am confused what is really a good way to parse this file. Can any one help me?

Edit: Here is what I have got. But I have created unnecessary array. I just want to skip till Uid. But I don't know how to.

  char temp[8][1024];

  struct FILE * pFile;

  pFile = fopen ("/proc/1/status","w+");


fscanf(pFile,"%[^\n] %[^\n] %[^\n] %[^\n] %[^\n] %[^\n] %s %s",temp[0],temp[1],temp[2],temp[3],temp[4],temp[5],temp[6],temp[7]);

printf(" User id %s \n",temp[7]);

Thanks

Upvotes: 0

Views: 887

Answers (1)

jfly
jfly

Reputation: 7990

You can read the file line by line with getline(it's part of c++, and a GNU extensions in C, not standard C) until you find the Uid, then stop:

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

int 
main(void)
{   
    FILE * fp; 
    char * line = NULL;
    size_t len = 0;
    ssize_t read;

    fp = fopen("/proc/20204/status", "r");
    if (fp == NULL)
        exit(EXIT_FAILURE);

    while ((read = getline(&line, &len, fp)) != -1) {
            char *content;
            content = strtok(line, ":");

            printf("content: %s\n", content);
            if(strncmp(content, "Uid", 3) == 0)
            {   
                    printf("get it:\n");
                    //get the User ID
                    printf("%s\n", strtok(NULL, ":"));
                    break;
            }   
       }  

    if (line)
        free(line);
    exit(EXIT_SUCCESS);
}

Upvotes: 2

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