Re: folder parsing (newbie)problem

On 22 Jan, 08:13, oswald.ha...@xxxxxxxxx wrote:

i am learning to parse directory using dirent.h (using gcc of cygwin
as compiler)

technically direct.h is off-topic. If your problem is with
dirent.h you need to take it to a unix news group.

But I'm not sure your problem is dirent.h...


and tried to make an array of names of .png files in a
directory
here my problem is with accessing a char* []
I wrote this function

int parsedirectory(char * dirname){
 struct dirent **filelist = {0};

you've initialised this as if it were a struct.
It's not it's a ptr.

use
struct dirent **filelist = NULL;

 char * directory =dirname;
 int fcount = -1;
 int i = 0;
 fcount = scandir(directory, &filelist, 0, alphasort);

 if(fcount < 0) {
  perror(directory);
  return 1;
 }

 int pngcnt;

you can't mix declarations with statements in C89
(the most portable standard).

 pngcnt=0;
 for(i = 0; i < fcount; i++)  {
//i want to check if filename has a .png in it
if(strstr(filelist[i]->d_name,".png")!=NULL){
   ++jpgcnt;
  }

 }
printf("png imgs:%d\n",pngcnt);//this shows totalnumber of .pngs

//then I can create a filenames array of size pngcnt

char* filenames[pngcnt];

this is an array of char*. Somewhere you must allocate some memory
for these pointers to point to. You don't.


//then i want to strcat the foldername with the imagename and add it
to the array
//so each entry in the array will be a string like
// "F:\code\c\testparse\man1.png"

beware of // comments. They screw up in postings

//but here i am stuck since the value fcount can't be used to
//index this array

I've no idea what this means.


//i tried like this

char fldr[strlen(dirname)];

you can't use strlen() as an array dimension. Does this
even compile? If so you are using a weird compiler.
(maybe gcc not in ANSI mode). Assume dirname is six characters.
Then strlen is 6.

strcpy(fldr,dirname);

oops! dirname actually occupies *7* bytes (one for the nul
char).

strcat(fldr,"\\");

oops!! you now have 8 bytes in your 6 byte array.
Use malloc()

char *fldr = malloc (strlen(dirname) + 2);
if (fldr == 0) abort();

int j; //this I use to index into filenames[]
j=0;
for(i=0;i<fcount;i++){
  if(strstr(filelist[i]->d_name,".png")!=NULL){
     char* name; //to make full name of a file
     char fldrtemp[strlen(fldr)];
     strcpy(fldrtemp,fldr);//so that strcat will not chang fldr
     name=strcat(fldrtemp,filelist[i]->d_name);

more of the same. Also you point name at fldrtemp[]
which disappears at the end of the for loop.
And then probably gets reused on the next iteration.
Use malloc().

char* name = malloc (strlen(fldr) + strlen(filelist[i]->d_name) +
1);
strcpy (fldrtemp, fldr);
name = strcat (fldrtemp,filelist[i]->d_name);

/* or replace the last two lines with
sprintf (name, "%s%s", fldr, filelist[i]->d_name);

     pngfilenames[j++]=name;
   }

}
}

my problem is that when i try to iterate thru pngfilenames using
for(i=0;i<pngcnt;i++){
  printf("%s\n",pngfilenames[i]);

}

i get something like
D"
D"
D"
D"
  not full path imagefilenames as expected!!
i am not sure if this is the right way..my c learning is in its
infancy so if

anyone can suggest a right way i will be grateful

a general suggestion is break the program down into
smaller steps. Write a program then returns all the files
in the directory. Print them out. Does that look ok?
Filter out the pngs. Print them

<OT>
you do know scandir() will do this for you?
</OT>

turn up your compiler warnings. If it's gcc
use
gcc -W -Wall -ansi -pedantic

and maybe -O2

you should probably read up on pointers and on malloc().

char *name[23];

defines an array of pointers. It *does not* allocate
any memory for the pointers to point at.


--
Nick Keighley

Quality: this activity has been delayed due to higher priority tasks.
.

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