equivalent to cut command in unix

[ahsanamin]

Hi,
I am very familiar with unix commands but not as familiar with C. Can anyone provide me a function in C which works similar to cut fuction in unix. The cut command is very useful for parsing strings. Basically my problem is that I have a string of characters delimited by colons ) and I would like my program to read each line and read the data in each field into a variable.
for example if the string is
1234:232:222
I would like to read 1234 into variable a, 232 into b and 222 into c.
Thanks
Ahsan

 

[olded]

Ahsan:

Unfortunately, the standard "C" libary doesn't contain a cut command, but the string tokenizer function, strtok should do the trick of splitting:

1234:232:222

into variables. What's unfortunate, is if you have a null field:

1234:232:::::222

That's why I have my own version of strtok called xstrtok. Here's an example using the pipe symbol, |, as a delimiter:

Regards,

Ed

#include <stdio.h>

/* example tokenizeing a string */

int main(argc,argv)
int argc;
char **argv;
{
char *xstrtok();
char *strtok();
char *string = &quot;a|string|of||tokens&quot;;
char *field1, *field2, *field3, *field4, *field5;

field1=xstrtok(string,&quot;|&quot;
field2=xstrtok(NULL, &quot;|&quot;
field3=xstrtok(NULL, &quot;|&quot;
field4=xstrtok(NULL, &quot;|&quot;
field5=xstrtok(NULL, &quot;|&quot;

printf(&quot;field 1 is %s\n&quot;, field1);
printf(&quot;field 2 is %s\n&quot;, field2);
printf(&quot;field 3 is %s\n&quot;, field3);
printf(&quot;field 4 is %s\n&quot;, field4); /* should be null */
printf(&quot;field 5 is %s\n&quot;, field5);

exit(0);
}

/*
* strtok version that handles null fields
*/
char *xstrtok(line, delims)
char *line, *delims;
{
static char *saveline = NULL;
char *p;
int n;

if(line != NULL)
saveline = line;

/*
*see if we have reached the end of the line
*/
if(saveline == NULL || *saveline == '\0')
return(NULL);
/*
*return the number of characters that aren't delims
*/
n = strcspn(saveline, delims);
p = saveline; /*save start of this token*/

saveline += n; /*bump past the delim*/

if(*saveline != '\0') /*trash the delim if necessary*/
*saveline++ = '\0';

return(p);
}

 

[gonzilla]

Hi,

Just a little error in the xstrok example. When you define a char * like this...

char *string = &quot;a|string|of||tokens&quot;;

You can't do this in your xstrok() function...

*saveline++ = '\0';

Initializing a char * makes this an an &quot;unnamed, static array of characters, which may be stored in read-only memory, which is why you can't safely modify it.&quot; (Taken from comp.lang.c Frequently Asked Questions -

http://www.eskimo.com/~scs/C-faq/q1.32.html)

So you should initialize the character string like this

char string[] = &quot;a|string|of||tokens&quot;;

This will allow you to modify the characters stored in there.

HTH -Tyler

 

[ahsanamin]

Thanks a lot guys for all your help. It will help me a lot with my program.
Thanks
Ahsan

 

[logic4fun]

hi Olded,
i checked ur function as u said for my question of parsing and it works fine on an AIX box. but when i am testing on a linux box it throws me a memseg error in xstrtok function at the following place

if(*saveline != '\0') /*trash the delim if necessary*/
*saveline++ = '\0';

do we need to add any check..

 

[logic4fun]

I thought i would rather put the above this way..the code works fine with XLC compiler and it throws the above Segmentation error with GCC compiler.

 

[Salem]

logic4fun, read gonzilla's reply about char* vs. char[]


--

http://www.catb.org/~esr/faqs/smart-questions.html

 

[logic4fun]

Sorry Salem..Didnt noticed that.

thanks