errno --perror() problem

**GanglyLamb** · 04-01-2003

I want to make a file that is in a map....
I open it this way.

Code:

FILE *myfile;
myfile=fopen(map,"w");
if(myfile==0){
   perror("\n");
   printf("Press a key to continue.\n");
   getch();
   exit(1);
   }

Now that works great as long as that map exists. I deleted the map and tried to run it and perror gave me an error. Is there a way that i can know wich error has been given. That way i would be able to see wether its a problem with the non-existent map or something else.
And then i would make the program create the map and then do the fopen thing again.
I know the error thing has something to do with errno ..its just how do i use errno. (my lib reference wasnt that clear IMO).

::edit::
whoops forgot to place code tags

BTW : map is data\\whatever_file_user_wants_to_open.whatever_ex tension_i_add

**GanglyLamb** · 04-01-2003

oops alrdy found it

Code:

#include <errno.h>

if(errno==ENOENT){
       /*make the dir again*/
       }

Scuse me for my stupidity

.

**Vber** · 04-01-2003

You're telling me that you aren't getting a error message telling that the file was not found? well here I tried and it gave me, "No such file or directory".

Code:

#include <stdio.h>

int main(void) {
	FILE *fp;

	if ((fp = fopen("lelelele.xxx","r")) == NULL) {
		perror("Fopen: ");
		return 0;
	}

	else {
		printf("We opened the file\n");
		printf("Aleluia\n");
		fclose(fp);
	}

	return 0;
}

**GanglyLamb** · 04-01-2003

yea yeah but it works over here its like this..;
the app asks for a file taht the user want to make user enters his filanem..... program adds a directory to it so that inthe end the user his file gets into data\hisfile.txt . But i solved it....Only thing is i was compiling and the compiler started acting pretty strange it was like this.

Code:

int a=4;
int lamb=6;

wasnt the same as

Code:

int lamb=6;
int a=4;

So i just shut down the comp opened the case and i saw that my cooling fan had stopped spinning.....
So i laid my hand on cpu and geesh i bet i can fry an egg on it.; so i hope my comp is still intact....

**Hammer** · 04-01-2003

Just for fun, here's an example showing how to collect error messages and report them later rather than immediately.

Code:

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

#define NUM_FILES 5

int main(void)
{
  FILE *fp[NUM_FILES];
  char Errors[NUM_FILES][BUFSIZ];
  int i;
    
  for (i = 0; i < NUM_FILES; i++)
  {
    char buf[BUFSIZ];
    sprintf (buf, "File%02d.txt", i);
    
    if ((fp[i] = fopen(buf, "r")) == NULL)
      sprintf (Errors[i], "%s FAILED : (%d) %s", buf, errno, strerror(errno));
    else sprintf (Errors[i], "%s OPEN\n", buf);
  }
  
  for (i = 0; i < NUM_FILES; i++)
  {
    printf ("Status of file %d: %s", i, Errors[i]);
  }
  
  for (i = 0; i < NUM_FILES; i++)
  {
    if (fp[i])
      fclose(fp[i]);
  }
  
  return 0;
}

/*
 * Output
 Status of file 0: File00.txt FAILED : (2) No such file or directory
 Status of file 1: File01.txt OPEN
 Status of file 2: File02.txt FAILED : (2) No such file or directory
 Status of file 3: File03.txt FAILED : (2) No such file or directory
 Status of file 4: File04.txt FAILED : (2) No such file or directory
 *
 */

**GanglyLamb** · 04-01-2003

Ive got another question -not related to errno or perror.
Its about spawn and his families.

I would like to display the content of a directory.
First i thought lets keep it siple and use system("dir data");
But that gives an output that is not very fancy.
So i was thinking bout spawn (mayb that would do the thing for me). If im alrdy wrong here then excuse me.

Anyway with spawn

Code:

/*main looks like this*/
int main(int argc, char filename[]);

/*then i make a call to a function in main*/
int play(filename[]);
/* in function play i do this*/
spawnvp(P_WAIT,data,filename[] );
/*But this gives me an error*/

So my question is am i on the right track with spawn and all of his families?
If so what can be wrong with that louzy piece of code?

::edit::
checked the new faq section and there was a thing related to this, but still...

**GanglyLamb** · 04-01-2003

Hmm figured out by now that spawn isnt made for that.
Instead i came up with this.....

Code:

#include <dir.h>
char buffer[MAXPATH];
getcwd(buffer, MAXPATH);
printf("The current directory is: %s\n", buffer);
char drive[MAXDRIVE];
char dir[MAXDIR];
char file[MAXFILE];
char ext[MAXEXT];
int flags;
char directory[]="\\data\\";
int buffer_length;
buffer_length=strlen(buffer);
for(int i=0;i<6;i++){
      buffer[buffer_length+i]=directory[i];
	}
printf("%s",buffer);
flags=fnsplit(buffer, drive, dir, file, ext);
if(flags && FILENAME && EXTENSION){
	printf("\n\n%s%s\n",file,ext);
	}

This may look like alternative coding but its the only way that i can come up with now to solve my problem.
So it takes the current directory and put it into buffer then i add a subdirectory data to buffer.... and then i try to split it in pieces with fnsplit. Normally i would see the file that is in <<buffer>>\data\ but output to screen is totally messed up....
Anyone who sees my mistake?

**Hammer** · 04-01-2003

Are you trying to do this

**GanglyLamb** · 04-01-2003

yup as i alrdy mentioned i looked into the faq. But i didnt really understood everything thats why i started trying to figure it out by myself.... (coz i dont like copy'n-paste).
Well ill copy'n paste it see what it actually does.... and look what the values are of FA_DIREC and ALL_ATTS....and only if i get whats going on ill put it in my code...

Guess ill have to take my blender to get a mixture of both things.

Thx anyway

**Hammer** · 04-01-2003

>>i didnt really understood everything thats why i started trying to figure it out by myself.... (coz i dont like copy'n-paste).
The idea behind the FAQ here is that it gives you enough information to take a snippet of code and make something with it. If you've read the FAQ, and can't understand the code/concept, let me know, and I'll try to add more of an explanation to it. There's no point in having the FAQ if doesn't answer your questions.

**GanglyLamb** · 04-01-2003

Well actually that faq made me thing bout the whole thing and i solved it without using any of the faq code. So to read files out of a directory that is constructed like this:

drive:\dir\subdir\my_app.exe
\data\data.txt

Where drive, dir and subdir are not the same on every system.
+there mayb several dirs and subdirs.

Code:

do{
	printf("Choose your quiz.\n");
	struct ffblk ffblk;
	int found;
	char directory1[]="DATA\\";
	char directory[]="\\DATA\\*.txt";
	char buffer[MAXPATH];
	char *quiz_file;
	char *extension;
	char name[BUFSIZ];
	getcwd(buffer, MAXPATH);
	strcat(buffer,directory);
	found=findfirst(buffer,&ffblk,0);
	while (!found)
	{
		if((quiz_file=strchr(ffblk.ff_name,'.'))!=NULL){
			*quiz_file=' ';
			*++quiz_file=' ';*++quiz_file='\0';
			strcpy(name,ffblk.ff_name);
			textcolor(14);/*RED*/
			cprintf("%s",name);
			}
			found = findnext(&ffblk);
		}

So in a way the faq was really good .. else i wouldnt know about functions like findfirst and findnext.

Keep up the good work (bout the faq), those questions really make me think bout something like how would i do that...

Thread: errno --perror() problem

Thread Tools

Search Thread

Display

errno --perror() problem

Similar Threads

how to clean errno?

errno function, error TLS/non TLS

/usr/bin/ld: errno: TLS definition in /lib/libc.so.6

Function argument assignment between types "unsigned int" and "unsigned long"

simulate Grep command in Unix using C