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string search and replace

P: n/a
Hi all,

Following is my attempt to write a string search and replace
function.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*-------------------------------------------------------------------------------------------
| Function name : strrep
|
| Arguments : src,find,rep
|
| src string should be *big* enough to hold the result
|
| Return Value : Number of replacements made |
--------------------------------------------------------------------------------------------*/
int strrep(char *src,const char *find,const char *rep)
{
char *remaining; /* pointer to the left over part
*/
int count = 0; /* no. of replacements
*/
size_t find_len = strlen(find); /* length of find string
*/
size_t rep_len = strlen(rep); /* length of replace string */

if(find_len == 0) return 0; /* nothing to find */

/*Initially allocate memory to store whole of src */
if( (remaining = malloc(strlen(src) + 1)) == NULL) /*remember to
free this*/
{
printf("Sorry out of memory !");
return 0;
}
while( (src = strstr(src,find)) != NULL ) /* get the matching
position */
{
count++; /*Count the num of
replacements*/
strcpy(remaining,src + find_len); /*store left over string
*/
strcpy(src,rep); /*make the
replacement */
src += rep_len; /*move to end of
replacement */
strcpy(src,remaining); /*copy back the left
over part */
}

free(remaining);
return count;
}
I know that this code is inefficient (it uses all the string
library routines),
I wanted to know how to improve this code. Can anyone help me ?
I want to know how you would implement the same function
I know that there are some Regex libraries to do this effectively.
But why is such a common function not there in standard library ?
Thanks for your time,
Yugi

Oct 11 '06 #1
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5 Replies


P: n/a

int main(void) wrote:
Hi all,

Following is my attempt to write a string search and replace
function.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*-------------------------------------------------------------------------------------------
| Function name : strrep
|
| Arguments : src,find,rep
|
| src string should be *big* enough to hold the result
|
| Return Value : Number of replacements made |
--------------------------------------------------------------------------------------------*/
int strrep(char *src,const char *find,const char *rep)
{
char *remaining; /* pointer to the left over part
*/
int count = 0; /* no. of replacements
*/
size_t find_len = strlen(find); /* length of find string
*/
size_t rep_len = strlen(rep); /* length of replace string */

if(find_len == 0) return 0; /* nothing to find */

/*Initially allocate memory to store whole of src */
if( (remaining = malloc(strlen(src) + 1)) == NULL) /*remember to
free this*/
{
printf("Sorry out of memory !");
return 0;
}
while( (src = strstr(src,find)) != NULL ) /* get the matching
position */
{
count++; /*Count the num of
replacements*/
strcpy(remaining,src + find_len); /*store left over string
*/
strcpy(src,rep); /*make the
replacement */
src += rep_len; /*move to end of
replacement */
strcpy(src,remaining); /*copy back the left
over part */
}

free(remaining);
return count;
}
I know that this code is inefficient (it uses all the string
library routines),
I wanted to know how to improve this code. Can anyone help me ?
I want to know how you would implement the same function
I know that there are some Regex libraries to do this effectively.
But why is such a common function not there in standard library ?
Thanks for your time,
Yugi

Sorry for that bad layout. This would be good.

Hi all,
Following is my attempt to write a string search and replace
function.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*---------------------------------------------------------------------------
| Function name : strrep
| Arguments : src,find,rep
| src string should be *big* enough to hold the result
| Return Value : Number of replacements made
----------------------------------------------------------------------------*/
int strrep(char *src,const char *find,const char *rep)
{
char *remaining; /*pointer to the left over part */
int count = 0; /* no.of replacements*/
size_t find_len = strlen(find);/*length of find string*/
size_t rep_len = strlen(rep);/*length of replace string*/

if(find_len == 0) return 0; /* nothing to find */

/*Initially allocate memory to store whole of src */
if( (remaining = malloc(strlen(src) + 1)) == NULL)
{
printf("Sorry out of memory !");
return 0;
}
/* get the matching position*/
while( (src = strstr(src,find)) != NULL )
{
count++; /*Count the num of replacements*/
strcpy(remaining,src + find_len); /*store left over string */
strcpy(src,rep); /*make the replacement*/
src += rep_len; /*move to end of replacement*/
strcpy(src,remaining); /*copy back the left over part*/
}

free(remaining);
return count;
}
I know that this code is inefficient (it uses all the string
library routines),
I wanted to know how to improve this code. Can anyone help me ?
I want to know how you would implement the same function
I know that there are some Regex libraries to do this effectively.
But why is such a common function not there in standard library ?
Thanks for your time,
Yugi

Oct 11 '06 #2

P: n/a

int main(void) wrote:
Hi all,

Following is my attempt to write a string search and replace
function.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*-------------------------------------------------------------------------------------------
| Function name : strrep
|
| Arguments : src,find,rep
|
| src string should be *big* enough to hold the result
|
| Return Value : Number of replacements made |
--------------------------------------------------------------------------------------------*/
int strrep(char *src,const char *find,const char *rep)
{
char *remaining; /* pointer to the left over part
*/
int count = 0; /* no. of replacements
*/
size_t find_len = strlen(find); /* length of find string
*/
size_t rep_len = strlen(rep); /* length of replace string */

if(find_len == 0) return 0; /* nothing to find */

/*Initially allocate memory to store whole of src */
if( (remaining = malloc(strlen(src) + 1)) == NULL) /*remember to
free this*/
{
printf("Sorry out of memory !");
return 0;
}
while( (src = strstr(src,find)) != NULL ) /* get the matching
position */
{
count++; /*Count the num of
replacements*/
strcpy(remaining,src + find_len); /*store left over string
*/
strcpy(src,rep); /*make the
replacement */
src += rep_len; /*move to end of
replacement */
strcpy(src,remaining); /*copy back the left
over part */
}

free(remaining);
return count;
}
I know that this code is inefficient (it uses all the string
library routines),
I wanted to know how to improve this code. Can anyone help me ?
I want to know how you would implement the same function
I know that there are some Regex libraries to do this effectively.
But why is such a common function not there in standard library ?
Thanks for your time,
Yugi

Sorry for that bad layout. This would be good.

Hi all,
Following is my attempt to write a string search and replace
function.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*---------------------------------------------------------------------------
| Function name : strrep
| Arguments : src,find,rep
| src string should be *big* enough to hold the result
| Return Value : Number of replacements made
----------------------------------------------------------------------------*/
int strrep(char *src,const char *find,const char *rep)
{
char *remaining; /*pointer to the left over part */
int count = 0; /* no.of replacements*/
size_t find_len = strlen(find);/*length of find string*/
size_t rep_len = strlen(rep);/*length of replace string*/

if(find_len == 0) return 0; /* nothing to find */

/*Initially allocate memory to store whole of src */
if( (remaining = malloc(strlen(src) + 1)) == NULL)
{
printf("Sorry out of memory !");
return 0;
}
/* get the matching position*/
while( (src = strstr(src,find)) != NULL )
{
count++; /*Count the num of replacements*/
strcpy(remaining,src + find_len); /*store left over string */
strcpy(src,rep); /*make the replacement*/
src += rep_len; /*move to end of replacement*/
strcpy(src,remaining); /*copy back the left over part*/
}

free(remaining);
return count;
}
I know that this code is inefficient (it uses all the string
library routines),
I wanted to know how to improve this code. Can anyone help me ?
I want to know how you would implement the same function
I know that there are some Regex libraries to do this effectively.
But why is such a common function not there in standard library ?
Thanks for your time,
Yugi

Oct 11 '06 #3

P: n/a
int main(void) wrote:

Sending the same message three times does not endear you to us.
Sending the same message thrre times does not endear you to us.
Sending the same message three times does not endeer you to us.
But why is such a common function not there in standard library ?
Likely:

Because search-and-replace may need to expand the target string,
and there isn't an obvious single best way to do this.

(And because there wasn't one commonly implemented when the first
standard was produced.)

--
Chris "Essen -8 and counting" Dollin
"A facility for quotation covers the absence of original thought." /Gaudy Night/

Oct 11 '06 #4

P: n/a

Chris Dollin wrote:
int main(void) wrote:

Sending the same message three times does not endear you to us.
Sending the same message thrre times does not endear you to us.
Sending the same message three times does not endeer you to us.
My apologies. I sent the second time because layout of the code
after
posting got srambled somehow.
I dont know why it got posted the third time.
I'm using google interface.
>
But why is such a common function not there in standard library ?

Likely:

Because search-and-replace may need to expand the target string,
and there isn't an obvious single best way to do this.

(And because there wasn't one commonly implemented when the first
standard was produced.)
Thanks for that point.
Thanks for your time,
Yugi.

Oct 11 '06 #5

P: n/a
"int main(void)" wrote:
Chris Dollin wrote:
>int main(void) wrote:
.... snip about string search and replace ...
>>
>>But why is such a common function not there in standard library ?

Likely:

Because search-and-replace may need to expand the target string,
and there isn't an obvious single best way to do this.

(And because there wasn't one commonly implemented when the first
standard was produced.)

Thanks for that point.
And because the function is rarely needed. It may be useful in
replacing strings during a file copy operation, which is a
different matter. It might be instructive to examine how
identifiers are replaced in id2id, for which see id2id-20.zip at:

<http://cbfalconer.home.att.net/download/>

--
Some informative links:
<news:news.announce.newusers
<http://www.geocities.com/nnqweb/>
<http://www.catb.org/~esr/faqs/smart-questions.html>
<http://www.caliburn.nl/topposting.html>
<http://www.netmeister.org/news/learn2quote.html>
<http://cfaj.freeshell.org/google/>
Oct 11 '06 #6

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Replies have been disabled for this discussion.