*** Search DIR for file name ***********

[DaniDak]

Hi

How can I do the following using C in UNIX.

I need to search a directory for a file and open that file.
The directory will contain log files and some other file, that have a file name of:
somename_DTS.log, DTS being date time stamp (20040429104607) when the file was created.
the only thing that is different between the log file names is the DTS.
What I need to do is to get the name of the newest file in the directory.
Is there anything in UNIX that I could use in my C program to find the newest file
and get its name. Or do I have to load all the files into an array than sort it and get the newest file name that way.

files that match
Thank you

 

[xwb]

You don't have to load in all the files: only the filenames and their details. Look up the man page on opendir, readdir and closedir.

Alternatively, since you have the names in such a convenient form, popen ("ls -1 | sort", "r") and start reading. It is more inefficient but will give you the names in some sort of order.

 

[itsgsd]

Here's an example illustrating what xwb suggested. It uses opendir,readdir,closedir and stat to get the info you need.

#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>

int main(void) {

  DIR *dir;
  struct dirent *ent;
  struct stat statbuf;
  time_t new_t=0;
  char new_n[100] = "";

  dir = opendir(".");

  while ((ent = readdir(dir)) != NULL) {
    if (strstr(ent->d_name,"_DTS")) { 
      stat(ent->d_name, &statbuf);
      if (statbuf.st_mtime > new_t) {
        strcpy(new_n,ent->d_name);
        new_t = statbuf.st_mtime;
      }
    }
  }

  printf("newest file is %s\n",new_n);
  closedir(dir);

  return 0;
}

Good luck.

 

[DaniDak]

Thanks for your information.
I really do appreciated.

 

[logic4fun]

Can somebody help me out if i need to read the last 10 oldest files from a directory without taking into array. The above gives the newest or the oldest.

Thanks for your help

 

[olded]

If you are going to use xwb's method using popen, then this command probably will work:

ls -1rt mydir|head -10

 

[logic4fun]

Is there a way to get this done using STAT and dirent structures. because i dont want to make a systemcall or popen call to ls -lrt.

 

[Salem]

Well basically, you take the itsgsd's answer and add this

time_t then;
time_t now = time(NULL);
struct tm tm_now = *localtime( &now );
tm_now.tm_mday -= 10;     /* 10 days ago */
then = mktime( &tm_now ); /* now we have a time_t for 10 days ago */

Then inside the loop, we simply have

if ( statbuf.st_mtime > then )
/* file is newer than 10 days old */

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