Help with Strtok() command.

[TheButcher]

Be prepared......I'm a newbie.

I have a problem. I have a file I have to read in and parse it depending upon white space.

Ex) #comment

I read this line in using fgets() into a string array. I then use an output pointer to do a string tokenizer.

After the eliminating the frontal white space(' ', \t, \n, \r), I want to check the 1st line to see if it is a comment. I can do this with an array(use array[0] to see if is '#'). But strtok() can only be done with a pointer. How do I check the 1st character of a pointer?

Maybe there is a better way to do this, but here is what I got.

while((!feof(FreadIn)) && (!(FileLine[0] == '.')))
{
fgets(FileLine, 100, FreadIn);
if ((FileLine[0] == ' ') || (FileLine[0] == '\t') || (FileLine[0] == '\n'))
{
strcpy(temp1, FileLine);
output1 = strtok(temp1, whitespace);
fputs(output1, Fintermediate);
fputc(' ', Fintermediate);
while((output1 = strtok(NULL, whitespace)) != NULL)
{
fputs(output1, Fintermediate);
fputc(' ', Fintermediate);
}
fputc(newLine, Fintermediate);
}
else if(FileLine[0] == '#')
{
fputs(FileLine, Fintermediate);
}
else if((FileLine[0] == '.') && (FileLine[1] == 'P'))
{
fputs(FileLine, Fintermediate);
}

1st...if there is space, tokenize it.
2nd...if 1st char is #, write it to file
3rd...if it is ".PROGRAM" go on to next section (not shown)



Thanks in advance!

 

[rbobbitt]

If I understand your intentions correctly, strtok() doesn't seem like it's the tool for the job.

Maybe something like this will do the trick:

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

#define MAX_LINE 100 /* or whatever's appropriate */
int
main(void)
{
FILE *fp=fopen(&quot;foo.txt&quot;,&quot;r&quot;
char line[MAX_LINE+1];

if (!fp) {
perror(&quot;fopen&quot;
} else {
char *ptr;
while (fgets(line,sizeof line,fp)) {
ptr=line;
/* Skip any leading white space */
while (isspace((unsigned char)*ptr)) {
++ptr;
}
if (*ptr=='#') {
/* it's a comment */
} else if (strcmp(ptr,&quot;.PROGRAM&quot==0) {
/* &quot;program&quot; */
} else {
/* regular line */
}
}
}
return 0;
}

BTW, an array of char can be passed to any function that expects a pointer to char. In a value context, an array becomes a pointer to its first element.
Russ
bobbitts@hotmail.com

http://home.earthlink.net/~bobbitts

 

[TheButcher]

Thank You Mr. Bobbiitts!!!

Okay, have a new problem.

i get file line,
FileLine = &quot;\t NAME\t BYTE\t $&quot;Your Name&quot;\t #comment

I read in this line and tokenize it by whitespace as I did above. I put the &quot;NAME&quot; and &quot;BYTE&quot; into a table. This is no problem.

Here is the problem. I need to check the $&quot; to see that it is a string($&quot;&quot and not a character($''). I tried using the string tokenizer with an array, but it gave me a core dump. So I am still using a pointer.

char FileLine[500];
char *output1;
char whitespace[] = &quot; \t\r\n&quot;;
output1 = strtok(temp1, whitespace);
while((output1 = strtok(NULL, whitespace)) != NULL)
{/*stuff in here*/}

output1 is a pointer, so I cant do:
output1[0] == '$' && output1[1] == '&quot;';

or can I?

Thanks again!

 

[rbobbitt]

I think I misunderstood where you wanted to use an array with strtok(). For the return value of strtok() you must use a pointer to char, as you are doing above.

if (output1[0] == '$' && output1[1] == '&quot;')

This is perfectly fine. You can use array subscripting on pointers.

The above can be written as you've done, or you can do this:

if (*output1=='$' && *(output1+1)=='&quot;')

In fact, the array subscript notation above gets converted to this form automatically by the compiler due to the fact that arrays become pointers to their first element in a value context. It's even legal to write the expression like this:

if (0[output1]=='$' && 1[output1]=='&quot;')

This expression will become:

if (*(0+output1)=='$' && *(1+output1)=='&quot;')

Because addition is commutative, it makes no difference.

All in all, the way you have it is probably the easiest to read.
Russ
bobbitts@hotmail.com

http://home.earthlink.net/~bobbitts

 

[TheButcher]

Russ,
You have saved me from the dreaded 'F'. Thank you once again!
Butch