Need to seperate input scanf()

E

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!
 
E

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;
Click to expand...

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!
Click to expand...

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
 
E

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();
 
E

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();
Click to expand...

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
 
F

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=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr,"abc"); */
}
return arr;
}

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

Regards,
Mohan S N
 
E

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=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr,"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr);
}
free(arr);
}
Click to expand...


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
 
E

Emmanuel Delahaye

(supersedes <[email protected]>)

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=(char*) malloc(STR_LENGTH*sizeof(char));
/* strcpy(arr,"abc"); */
}
return arr;
}

int main(void)
{
int i=0
char** arr=retStrArr();
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr);
}
free(arr);
}
Click to expand...


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 = malloc (STR_LENGTH * sizeof *arr);
sprintf (arr, "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);
free (arr);
}
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."
 
B

Barry Schwarz

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*));
Click to expand...

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=(char*) malloc(STR_LENGTH*sizeof(char));
Click to expand...


Doyouenjoyreadinglongsentenceswithnospaces?

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

int main(void)
{
int i=0
char** arr=retStrArr();
Click to expand...


You need to check the return from the function to determine if it
succeeded.
for(i=0;i<NUM_OF_STRINGS;i++)
{
free(arr);
}
free(arr);
}
Click to expand...



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