Need to seperate input scanf()

[ern]

I'm using scanf("%s",userInput) to capture up to three words from the
user. I want to seperate those three words into three variables:

char * firstWord;
char * secondWord;
char * thirdWord;

Is there an easy way/function that can do this already? Thanks!

[Emmanuel Delahaye]

ern wrote on 20/09/05 :

I'm using scanf("%s",userInput) to capture up to three words from the
user. I want to seperate those three words into three variables:

char * firstWord;
char * secondWord;
char * thirdWord;
These variables are just uninitialized pointers. If you insist in using
scanf(), you probably want a static or dynamic array of char.
Is there an easy way/function that can do this already? Thanks!

fgets() and a hand made parser using strchr(), strstr() etc.

Of course, there is a strtok() function that can be used to separate
tokens, but it has many caveats.

I think that POSIX.1 defines strtok_r() and strsep() that are better.
But they are not standard and probably not portable everywhere.

http://www.hmug.org/man/3/strtok_r.php
--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"It's specified. But anyone who writes code like that should be
transmogrified into earthworms and fed to ducks." -- Chris Dollin CLC

[ern]

Isn't fgets() for files? I want to read from STDIN.

[Emmanuel Delahaye]

ern wrote on 20/09/05 :

Isn't fgets() for files? I want to read from STDIN.

I guess you meant stdin. fgets() is for stream. Surprise, stdin *is* a
stream.

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"It's specified. But anyone who writes code like that should be
transmogrified into earthworms and fed to ducks." -- Chris Dollin CLC

[ern]

thanks. fgets and strtoks work pretty good. one more thing... how can
I return an array of strings? I'd imagine the syntax would be
something like:

char *[ ] myFunction();

[Emmanuel Delahaye]

ern wrote on 20/09/05 :

thanks. fgets and strtoks work pretty good. one more thing... how can
I return an array of strings? I'd imagine the syntax would be
something like:

char *[ ] myFunction();

No. There is no way to return an array in C[1]. All you can do is to
return the address of the first element of some array. (but you neeed a
way to know the limit : size, sentinel...).

Note that the returned address must be valid after the leaving from the
function. Hence, addresses local to the callee (called ?) are
forbidden.

-----------------
[1] However, you can return a copy of a structure holding an array, but
it's ugly and and more seriously inefficient and even unsafe if the
size is big....

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

..sig under repair

[Frodo Baggins]

I would like to know if this code snippet effectively allocates and
deallocates mem for the 2-D arr
char** retStrArr(void)
{
char** arr;
int i=0;
arr = (char**) malloc(NUM_OF_STRINGS*sizeof(char*));
for(i=0;i<NUM_OF_STRINGS;i++)
{
arr[i]=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr[i],"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr[i]);
}
free(arr);
}

Regards,
Mohan S N

[Emmanuel Delahaye]

Frodo Baggins wrote on 21/09/05 :

I would like to know if this code snippet effectively allocates and
deallocates mem for the 2-D arr

char** retStrArr(void)
{
char** arr;
int i=0;
arr = (char**) malloc(NUM_OF_STRINGS*sizeof(char*));
for(i=0;i<NUM_OF_STRINGS;i++)
{
arr[i]=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr[i],"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr[i]);
}
free(arr);
}

My compiler just told me that there is something wrong with your code :

main.c:8: warning: no previous prototype for 'retStrArr'
main.c: In function `retStrArr':
main.c:11: error: implicit declaration of function `malloc'
main.c:11: warning: nested extern declaration of `malloc'
<internal>:0: warning: redundant redeclaration of 'malloc'

main.c:11: error: `NUM_OF_STRINGS' undeclared (first use in this
function)
main.c:11: error: (Each undeclared identifier is reported only once
main.c:11: error: for each function it appears in.)
main.c:14: error: `STR_LENGTH' undeclared (first use in this function)

main.c: In function `main_':

main.c:23: error: syntax error before "char"
main.c:24: error: `NUM_OF_STRINGS' undeclared (first use in this
function)
main.c:26: error: implicit declaration of function `free'
main.c:26: warning: nested extern declaration of `free'
main.c:26: error: `arr' undeclared (first use in this function)
main.c:28: warning: nested extern declaration of `free'
main.c:26: warning: redundant redeclaration of 'free'
main.c:26: warning: previous implicit declaration of 'free' was here

Please provide a compiling code if you want an evaluation...

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"It's specified. But anyone who writes code like that should be
transmogrified into earthworms and fed to ducks." -- Chris Dollin CLC

[Emmanuel Delahaye]

(supersedes <mn***********************@YOURBRAnoos.fr>)

Frodo Baggins wrote on 21/09/05 :

I would like to know if this code snippet effectively allocates and
deallocates mem for the 2-D arr

char** retStrArr(void)
{
char** arr;
int i=0;
arr = (char**) malloc(NUM_OF_STRINGS*sizeof(char*));
for(i=0;i<NUM_OF_STRINGS;i++)
{
arr[i]=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr[i],"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr[i]);
}
free(arr);
}

My compiler just told me that there is something wrong with your code :

main.c:8: warning: no previous prototype for 'retStrArr'
main.c: In function `retStrArr':
main.c:11: error: implicit declaration of function `malloc'
main.c:11: warning: nested extern declaration of `malloc'
<internal>:0: warning: redundant redeclaration of 'malloc'

main.c:11: error: `NUM_OF_STRINGS' undeclared (first use in this
function)
main.c:11: error: (Each undeclared identifier is reported only once
main.c:11: error: for each function it appears in.)
main.c:14: error: `STR_LENGTH' undeclared (first use in this function)

main.c: In function `main_':

main.c:23: error: syntax error before "char"
main.c:24: error: `NUM_OF_STRINGS' undeclared (first use in this
function)
main.c:26: error: implicit declaration of function `free'
main.c:26: warning: nested extern declaration of `free'
main.c:26: error: `arr' undeclared (first use in this function)
main.c:28: warning: nested extern declaration of `free'
main.c:26: warning: redundant redeclaration of 'free'
main.c:26: warning: previous implicit declaration of 'free' was here

Please provide a compiling code if you want an evaluation...

Once fixed, and secured, the code is fine :

#include <stdlib.h>

#define NUM_OF_STRINGS 4
#define STR_LENGTH 32

static char **retStrArr (void)
{
char **arr = malloc (NUM_OF_STRINGS * sizeof *arr);

if (arr != NULL)
{
int i = 0;

for (i = 0; i < NUM_OF_STRINGS; i++)
{
arr[i] = malloc (STR_LENGTH * sizeof *arr[i]);
sprintf (arr[i], "abc%d", i);
}
}
return arr;
}

int main (void)
{
char **arr = retStrArr ();

if (arr != NULL)
{
int i = 0;
for (i = 0; i < NUM_OF_STRINGS; i++)
{
printf ("%s\n", arr[i]);
free (arr[i]);
}
free (arr);
}
return 0;
}

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"There are 10 types of people in the world today;
those that understand binary, and those that dont."

[Barry Schwarz]

On 21 Sep 2005 10:09:32 -0700, "Frodo Baggins" <fr*********@gmail.com>
wrote:

I would like to know if this code snippet effectively allocates and
deallocates mem for the 2-D arr
char** retStrArr(void)
{
char** arr;
int i=0;
arr = (char**) malloc(NUM_OF_STRINGS*sizeof(char*));
You did specify effective.

Don't cast the return from malloc. The only thing it does is
prevent the compiler from warning you about undefined behavior if you
forget to include a prototype for malloc.

Check the return from malloc. You need to know if it succeeded.
for(i=0;i<NUM_OF_STRINGS;i++)
{
arr[i]=(char*) malloc(STR_LENGTH*sizeof(char));
Doyouenjoyreadinglongsentenceswithnospaces?

sizeof(char) will always be 1.
/* strcpy(arr[i],"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
You need to check the return from the function to determine if it
succeeded.
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr[i]);
}
free(arr);
}

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