trim function dumping core

[rkk]

Hi,

I've written a small trim function to trim away the whitespaces in a
given string. It works well with solaris forte cc compiler, but on
mingw/cygwin gcc it isn't. Here is the code:

char *trim(char *s)
{
char *begin,*end;
begin = s;
/* ltrim start */
while(*begin != '\0') {
if(isspace(*beg in)) {
begin++;
} else {
s = begin;
break;
}
}
/* ltrim end */

/* rtrim start */
end = s + strlen(s) -1;
while( end !=s && isspace(*end) ) {
end--;
}
printf("%c\n",* end);
*(end+1) = '\0';
while(*s && isspace(*s)) s++;
/* rtrim end */
return s;
}

It is failing in the line having the code *(end+1) = '\0';. I think it
may be due to portablility issues & I need this code to work on all
well known platforms & compilers. Any sugesstions/help please?

Thank you.

Regards
Kalyan

[rkk]

Dear Mr.Joe,
Thanks for your code.

Regards
RKK
On Dec 7, 6:19 am, Joe Wright <joewwri...@com cast.netwrote:

rkk wrote:

Hi,

I've written a small trim function to trim away the whitespaces in a
given string. It works well with solaris forte cc compiler, but on
mingw/cygwin gcc it isn't. Here is the code:

char *trim(char *s)
{
char *begin,*end;
begin = s;
/* ltrim start */
while(*begin != '\0') {
if(isspace(*beg in)) {
begin++;
} else {
s = begin;
break;
}
}
/* ltrim end */

/* rtrim start */
end = s + strlen(s) -1;
while( end !=s && isspace(*end) ) {
end--;
}
printf("%c\n",* end);
*(end+1) = '\0';
while(*s && isspace(*s)) s++;
/* rtrim end */
return s;
}

It is failing in the line having the code *(end+1) = '\0';. I think it
may be due to portablility issues & I need this code to work on all
well known platforms & compilers. Any sugesstions/help please?Here's mine..

/*************** *************** *************** *************** ********
Program: trim.c
Author: Joe Wright
Date: 12/06/2006

rtrim() and ltrim() functions a la dBASE modify string in place.

*************** *************** *************** *************** *********/

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

#define length 256 /* Limit lines to 255 characters */
#define trim rtrim /* trim() is synonomous with rtrim() */

/* Remove trailing whitespace */

char * rtrim(char *str) {
char *s, *p; int c;
s = p = str;
while ((c = *s++)) if (!isspace(c)) p = s;
*p = '\0';
return str;

}/* Remove leading whitespace */

char * ltrim(char *str) {
char *s, *p;
for (s = p = str; *s && isspace(*s); s++) ;
while ((*p++ = *s++)) ;
return str;

}/* Combination of the two */

char * alltrim(char *str) {
return rtrim(ltrim(str ));

}/* A modest test */

int main(int argc, char **argv) {
char str[length];

if (argc != 2) {
printf("Usage: trim ' Try something like this. '\n");
return 0;
}

if (strlen(argv[1]) length-1) {
printf("Input String Too Long!\n");
return 0;
}
strcpy(str, argv[1]);
printf(" Input: Length %2d '%s'\n", (int)strlen(str ), str);

ltrim(str);
printf(" ltrim: Length %2d '%s'\n", (int)strlen(str ), str);

strcpy(str, argv[1]);
rtrim(str);
printf(" rtrim: Length %2d '%s'\n", (int)strlen(str ), str);

strcpy(str, argv[1]);
alltrim(str);
printf("alltrim : Length %2d '%s'\n", (int)strlen(str ), str);

return 0;}/* End of trim.c */

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[raxitsheth2000]

Joe/rkk,

check following main with your ltrim/rtrim/trim/trim_all...

int main()
{
char *p=NULL;
ltrim(p);

rtrim(p);

return 0;
}

I am not sure what should be the behaviour of l/r/all trim against NULL
ptr, on my sys is Seg Fault.(I am knowing why)

Should we check ?

char* (l/r) trim (char *s)
{
if (s==NULL) return NULL;
your remaining code of ltrim/rtrim;
}

this will ensure that your trim function is stable against one more
type of Bad-Input, (like one more testcase)
Even it is more likely that program may crash, but not in
ltrim/rtrim/all_trim written by you.

any thought on this ?
--raxit sheth

[Chris Dollin]

Richard Heathfield wrote:

santosh said:

>trm wrote:

>>What happens here?

#include <string.h>
int main ( void )
{
strlen(NULL);
return 0;
}

Possibly anything. It invokes undefined behaviour.

And what happens if someone asks a rhetorical question in comp.lang.c?

Someone points out that rhetoric is off-topic, don't they?

--
Chris "Perikles triumphant" Dollin
"A facility for quotation covers the absence of original thought." /Gaudy Night/

[santosh]

Keith Thompson wrote:

Richard Heathfield <rj*@see.sig.in validwrites:
[...]

And what happens if someone asks a rhetorical question in comp.lang.c?

Some idiot invariably answers it.

So you're implying obtusely that I'm an idiot?

[Keith Thompson]

"santosh" <sa*********@gm ail.comwrites:

Keith Thompson wrote:

>Richard Heathfield <rj*@see.sig.in validwrites:
[...]

And what happens if someone asks a rhetorical question in comp.lang.c?

Some idiot invariably answers it.

So you're implying obtusely that I'm an idiot?

I'm not going to answer that. 8-)}

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Richard Heathfield]

santosh said:

Keith Thompson wrote:

>Richard Heathfield <rj*@see.sig.in validwrites:
[...]

And what happens if someone asks a rhetorical question in comp.lang.c?

Some idiot invariably answers it.

So you're implying obtusely that I'm an idiot?

It is possible to infer that Keith is being self-deprecatingly self-mocking,
and in fact that is what I inferred when I read his reply. Don't jump at
shadows!

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[Keith Thompson]

Richard Heathfield <rj*@see.sig.in validwrites:

santosh said:

>Keith Thompson wrote:

>>Richard Heathfield <rj*@see.sig.in validwrites:
[...]
And what happens if someone asks a rhetorical question in comp.lang.c?

Some idiot invariably answers it.

So you're implying obtusely that I'm an idiot?

It is possible to infer that Keith is being self-deprecatingly
self-mocking, and in fact that is what I inferred when I read his
reply.

It is, in fact, certain.

Don't jump at shadows!

I assumed that santosh was *probably* joking. I wasn't certain, which
is why I added a smiley to my reply. But to be as clear as possible,
no serious insult was intended, and any non-serious insult was
directed only at myself. (*I* was the idiot who was answering a
rhetorical question.)

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Joe Wright]

ra************@ yahoo.co.in wrote:

Joe/rkk,

check following main with your ltrim/rtrim/trim/trim_all...

int main()
{
char *p=NULL;
ltrim(p);

rtrim(p);

return 0;
}

I am not sure what should be the behaviour of l/r/all trim against NULL
ptr, on my sys is Seg Fault.(I am knowing why)

Should we check ?

char* (l/r) trim (char *s)
{
if (s==NULL) return NULL;
your remaining code of ltrim/rtrim;
}

this will ensure that your trim function is stable against one more
type of Bad-Input, (like one more testcase)
Even it is more likely that program may crash, but not in
ltrim/rtrim/all_trim written by you.

any thought on this ?
--raxit sheth

String functions should behave gracefully when given strings to deal
with. Even zero length strings. It is up to the caller to ensure against
NULL pointers passed to string functions, IMO.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[pete]

Joe Wright wrote:

>
ra************@ yahoo.co.in wrote:

Joe/rkk,

check following main with your ltrim/rtrim/trim/trim_all...

int main()
{
char *p=NULL;

String functions should behave gracefully when given strings to deal
with. Even zero length strings.
It is up to the caller to ensure against
NULL pointers passed to string functions, IMO.

That's the way it is with the string functions
in the standard library.

--
pete

[rkk]

Sheth,

Yes you are right.
The code check for NULL should be done in ltrim,trim & rtrim functions.

Regards
RKK

ra************@ yahoo.co.in wrote:

Joe/rkk,

check following main with your ltrim/rtrim/trim/trim_all...

int main()
{
char *p=NULL;
ltrim(p);

rtrim(p);

return 0;
}

I am not sure what should be the behaviour of l/r/all trim against NULL
ptr, on my sys is Seg Fault.(I am knowing why)

Should we check ?

char* (l/r) trim (char *s)
{
if (s==NULL) return NULL;
your remaining code of ltrim/rtrim;
}

this will ensure that your trim function is stable against one more
type of Bad-Input, (like one more testcase)
Even it is more likely that program may crash, but not in
ltrim/rtrim/all_trim written by you.

any thought on this ?
--raxit sheth