strtok problem - strcmp

[collinm]

hi

this is my code to analyse a file

void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */

}
}
that work fine

now i want to compare the token string, i do:
void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */

if(strcmp(token ptr,"HLD")==0)
printf("hold\n" );
}
}

i get a segmentation fault

any idea?

[Eric Sosman]

collinm wrote:

[...]
now i want to compare the token string, i do:
void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */

if(strcmp(token ptr,"HLD")==0)
printf("hold\n" );
}
}

i get a segmentation fault

Do the strcmp() *before* strtok().

--
Er*********@sun .com

[Michael Mair]

collinm wrote:

hi

this is my code to analyse a file

void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */

}
}
that work fine

now i want to compare the token string, i do:
void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */
tokenptr will be NULL in the very last loop iteration at this
point; thus, using it after this line will give you undefined
behaviour (and in your case, luckily, a segfault).
Put the call to strtok() at the end of the loop.

I have not looked to closely at your code nor tested it.

--Michael
if(strcmp(token ptr,"HLD")==0)
printf("hold\n" );
}
}

i get a segmentation fault

any idea?

--
E-Mail: Mine is an /at/ gmx /dot/ de address.

[John Valko]

collinm wrote:

void analyzeFilename ()
{
char string[]="B_L2_HLD_GRN_ NOR_Run_Counter .txt";
char *tokenptr;
char *seperators="_" ;

tokenptr = strtok(string,s eperators); /* get the first token
*/
while (tokenptr != NULL) /* while more tokens in
strng */
{
printf("\t%s\n" ,tokenptr); /* print first token */
tokenptr = strtok(NULL,sep erators); /* get next token */
Consider the condition that breaks your loop -- when strtok returns
NULL. But before that condition is reached, you use the returned value
without checking it. My guess is that it's returning NULL and then
you're passing the NULL to strcmp() which causes the segmentation fault.
if(strcmp(token ptr,"HLD")==0)
printf("hold\n" );
}
}

i get a segmentation fault

any idea?

hope that helps,
John

[Mark McIntyre]

On 24 Mar 2005 09:22:36 -0800, in comp.lang.c , "collinm"
<co*****@laboit eaprog.com> wrote:

tokenptr = strtok(NULL,sep erators); /* get next token */
if strtok returned NULL here...
if(strcmp(token ptr,"HLD")==0)

.....this will segfault

you need to check for NULL before using the pointer
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >