ANSI C splitting string - c

Question

Hey there!
I'm stuck on an ANSI C problem which I think should be pretty trivial (it is at least in any modern language :/).
The (temporary) goal of my script is to split a string (array of char) of 6 characters ("123:45") which represents a timestamp minutes:seconds (for audio files so it's ok to have 120 minutes) into just the minutes and just the seconds.
I tried several approaches - a general one with looking for the ":" and a hardcoded one just splitting the string by indices but none seem to work.
void _splitstr ( char *instr, int index, char *outstr ) {
char temp[3];
int i;
int strl = strlen ( instr );
if ( index == 0 ) {
for ( i = 0; i < 3; ++i ) {
if ( temp[i] != '\0' ) {
temp[i] = instr[i];
}
}
} else if ( index == 1 ) {
for ( i = 6; i > 3; i-- ) {
temp[i] = instr[i];
}
}
strcpy ( outstr, temp );
}
Another "funny" thing is that the string length of an char[3] is 6 or 9 and never actually 3. What's wrong with that?

Answer 1

How about using sscanf(). As simple as it can get.
char time[] = "123:45";
int minutes, seconds;
sscanf(time, "%d:%d", &minutes, &seconds);
This works best if you can be sure that time string syntax is always valid. Otherwise you must add check for that. On success, sscanf function returns the number of items succesfully read so it's pretty easy to detect errors too.
Working example: http://ideone.com/vVoBI

Answer 2

How about...
int seconds, minutes;
minutes = atoi(instr);
while(*instr != ':' && *++instr != '\0');
seconds = atoi(instr);
Should be pretty fast.

Answer 3

You have basically three options
change the input string (can't be a string literal)
copy data to output strings (input can be a literal)
transform sequences of characters to numbers
Changing the input string implies transforming "123:45" to "123\0" "45" with an embedded null.
Copying data implies managing storage for the copy.
Transforming sequences of characters implies using, for example, strtol.

Answer 4

You aren't putting a terminating null on your string in temp[], so when you do a strlen(temp), you are accessing arbitrary memory.
Using your known lengths, you can use something like this:
char temp[4];
if (index==0)
{
strncpy(temp, instr, 3);
temp[3] = 0;
}
else if (index==1)
{
strncpy(temp, instr+4, 2);
temp[2] = 0;
}
strcpy(outstr, temp);
But, I'll caution that I've skipped all sorts of checking for valid lengths in instr and outstr.

Answer 5

you can try something like that:
void break_string(const char* input, char* hours, char* minutes)
{
if(input == 0 || hours == 0 || minutes == 0)
return;
while(*input != ':')
*hours++ = *input++;
*hours = '\0';
++input;
while(*minutes++ = *input++);
return;
}
Here is the same function a bit simplified:
void break_string(const char* input, char* hours, char* minutes)
{
if(input == 0 || hours == 0 || minutes == 0)
return;
while(*input != ':')
{
*hours = *input;
++hours;
++input;
}
*hours = '\0';
++input; //ignore the ':' part
while(*input)
{
*minutes = *input;
++minutes;
++input;
}
*minutes = '\0';
return;
}
int main()
{
char* test = "123:45";
char* minutes = malloc( sizeof(char) * 12 );
char* hours = malloc( sizeof(char) * 12 );
break_string( test , hours , minutes );
printf("%s , %s \n" , hours , minutes );
//...
free( minutes );
free( hours ) ;
}

Answer 6

This?
char *mins, *secs;
mins = str;
while(*(++str) != ':');
str[0] = '\0';
secs = s + 1;

Answer 7

Here's one way, I have ignore the "index" argument above:
#include <stdio.h>
#include <string.h>
void _splitstr ( char *instr, char *outstr ) {
char temp[10];
char* end = strchr(instr, ':');
int i = 0;
if(end != 0) {
while(instr != end)
temp[i++] = *instr++;
temp[i] = '\0';
strcpy(outstr, temp);
} else {
outstr = '\0';
}
}