fork download
copy 
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. // This function counts the number of digit places in 'pid'
  6. int pid_digit_places(int pid)
  7. {
  8.     int n = pid;
  9.     int places = 0;
  10.     while (n)
  11.         n /= 10;
  12.         places++;
  13.     return places;
  14. }
  15.  
  16. char *construct_path(int pid, char *dir)
  17. {
  18.     // get count of places in pid
  19.     int places = pid_digit_places(pid); 
  20.     char *pid_str = calloc(places, sizeof(char)); 
  21.  
  22.     // create string of pid 
  23.     sprintf(pid_str, "%d", pid); 
  24.  
  25.     char *proc = "/proc/";
  26.     size_t plen = strlen(proc);
  27.     size_t dlen = strlen(dir) + 1;
  28.     char *path = calloc(plen + dlen + places, sizeof(char));
  29.  
  30.     strcat(path, proc);
  31.     strcat(path, pid_str);
  32.     strcat(path, dir);
  33.  
  34.     return path;
  35. }
  36.  
  37. void fd_walk(int pid)
  38. {
  39.     char *fd = "/fd/";
  40.     char *fdpath = construct_path(pid, fd);
  41.  
  42.     // prints "/proc/573/fd/ - as expected    
  43.     printf("Before: %s\n", fdpath); 
  44.  
  45.     // shows a length of 13
  46.     printf("Size Before: %d\n", (int)strlen(fdpath));  
  47.  
  48.  
  49.     char *test = calloc(strlen(fdpath) + 1, sizeof(char));
  50.     strcpy(test, fdpath);
  51.  
  52.     // prints "/proc/573/fd" no trailing "/"
  53.     printf("Copied Str: %s\n", test); 
  54.  
  55.     //shows a length of 13 though
  56.     printf("Copied Size: %d\n", (int)strlen(test)); 
  57.  
  58.     // prints "/proc/573/fd" no trailing "/" now    
  59.     printf("After: %s\n", fdpath); 
  60.  
  61.     // still shows length of 13
  62.     printf("Size After: %d\n", (int)strlen(fdpath));         
  63. }
  64.  
  65. int main(void)
  66. {
  67.     // integer to create path around
  68.     int pid = 573; 
  69.     fd_walk(pid);
  70.     return 0;
  71. }
Success #stdin #stdout 0s 2424KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Before: /proc/573/fd/
Size Before: 13
Copied Str: /proc/573/fd
Copied Size: 13
After: /proc/573/fd
Size After: 13
https://ideone.com/k6kgoS
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!