topic Re: Using C to check file patten on directory in Operating System - Linux

Using C to check file patten on directory

Henry Chua — Mon, 17 Jul 2006 09:13:59 GMT

Hi Guys,

Just wondering is it possible to use C program to check whether files with certain pattern exists on a directory i.e. similar to using "ls pattern*"

regards
Henry

Re: Using C to check file patten on directory

A. Clay Stephenson — Mon, 17 Jul 2006 09:21:24 GMT

Of course it is possible. How do you think the ls command ultimately does it? On the other hand, why reinvent the wheel when a:
File *f;
f = popen("ls xyz*","r");
would do the trick for you.

If you really want to do this then you use opendir() to open a directory, readdir() to read each directory entry, and then use the regcomp() and related functions for RE matching. Man regcomp for details.

Re: Using C to check file patten on directory

TwoProc — Mon, 17 Jul 2006 09:21:37 GMT

Yes, possible in plenty, plenty of ways.

As many ways as you care to write a string matching algorithm.

Re: Using C to check file patten on directory

James R. Ferguson — Mon, 17 Jul 2006 09:22:47 GMT

Hi Henry:

Pattern matching uses regular expressions. This is easily done with 'Perl', 'awk' and 'sed'. If you would be more specific it would be easy to help.

Regards!

...JRF...

Re: Using C to check file patten on directory

Peter Nikitka — Mon, 17 Jul 2006 09:31:02 GMT

Hi,

of course regcomp()/regexec() is the interface that can do all the regular expression stuff.

But:
- if you need just the matching of a string like "ls fixedstring*", a simple strstr() in your readdir()-loop will do it.
- the regcmp()-pattern are that you use in grep, vi, .... These are NOT identical with the pattern in (k|c|tc)sh for filename globbing.

mfG Peter

Re: Using C to check file patten on directory

Henry Chua — Mon, 17 Jul 2006 10:06:38 GMT

Thanks for the tips.. if I am using popen(), is there anyway to redirect the error message so that it will not show up on the screen? =)

Re: Using C to check file patten on directory

Peter Nikitka — Mon, 17 Jul 2006 10:08:22 GMT

Hi,

act just as you would do in normal shell command, e.g.

f = popen("ls xyz* 2>/dev/null","r");

mfG Peter