splitting the lines in a file and compare the array element - c

Question

I have written the following code to split the lines, in which the strings are separated by symbol '#', and storing in the array named as'buf' here. This code is working fine if I am comparing any string present in the array[0] . but If I try to find the string present in array[3] for example here as 'admin', then it is having error as 'segmentation fault' . Could anyone help me to find why this code is not comparing any other argument.
I would be very thankful for this.
char **strsplit(const char* str, const char* delim, size_t* numtokens) {
char *s = strdup(str);
size_t tokens_alloc = 1;
size_t tokens_used = 0;
char **tokens = calloc(tokens_alloc, sizeof(char*));
char *token, *rest = s;
while ((token = strsep(&rest, delim)) != NULL) {
if (tokens_used == tokens_alloc) {
tokens_alloc *= 2;
tokens = realloc(tokens, tokens_alloc * sizeof(char*));
}
tokens[tokens_used++] = strdup(token);
}
if (tokens_used == 0) {
free(tokens);
tokens = NULL;
} else {
tokens = realloc(tokens, tokens_used * sizeof(char*));
}
*numtokens = tokens_used;
free(s);
return tokens;
}
The main() is as follows:
int main(void) {
char *line = NULL;
size_t linelen;
char **tokens;
size_t numtokens;
int ret=1;
FILE *ptr_file;
char buf[1000];
system("rm -rf input1.txt");
system("/www/stest/mds1 > input1.txt");
ptr_file =fopen("/www/stest/input1.txt","r");
if (!ptr_file)
return 1;
while (fgets(buf,1000, ptr_file)!=NULL)
{
tokens = strsplit(buf, "#\n", &numtokens);
size_t i;
for ( i = 0; i < numtokens; i++)
{
ret=strcmp(tokens[3],"member");
if(ret==0)
{
printf("%s",buf);
break;
}
}
fclose(ptr_file);
return 0;
return EXIT_SUCCESS;
}
Here is the output of the above code and I am having error if I want to print the lines which has 'member'as the third argument of the array.
abc#google.com#abdu#admin
abc#rediff.com#savya#cashier
abc#yahoo.com.com#andy#member
abc#google.com#susan#group
abc#facebook.com#andre#admin
Thanks.

Answer 1

I suspect what you want is something like this:
tokens = strsplit(buf, "#\n", &numtokens);
if(numtokens >= 4 && strcmp(tokens[3],"member") == 0)
{
printf("%s",buf);
}
As shown in George Houpis's answer it would also be good to double-check that strsplit does not return a null pointer.

Answer 2

This is not an answer, but the comment is not big enough. If you run this as your main, what is the output?
int main( int argc, char ** argv )
{
FILE * fin = fopen( "/www/stest/input1.txt", "rt" );
if( !fin )
return 1;
char buffer[1000];
while( fgets( buffer, 1000, fin ) )
{
size_t token_count;
char ** tokens = strsplit( buffer, "#\n", &token_count );
if( tokens )
{
size_t index;
for( index = 0; index < token_count; ++index )
if( !strcmp( tokens[index], "member" ) )
printf( "%d: %s | %s", index, tokens[index], buffer );
for( index = 0; index < token_count; ++index )
free( tokens[index] );
free( tokens );
}
}
fclose( fin );
return 0;
}
When I run with those 5 lines in the text file, I get:
3: member | abc#yahoo.com.com#andy#member
EDIT:
You can tokenize the string without malloc by keeping a second buffer and using pointers to that (still uses memory on the stack).
int main( int argc, char ** argv )
{
FILE * fin = fopen( argv[1], "rt" );
if( !fin )
return 1;
char buffer[1000];
while( fgets( buffer, 1000, fin ) )
{
char buffer_copy[1000];
strcpy( buffer_copy, buffer );
char * tokens[1000];
size_t token_count = 0;
char * ptr = tokens[token_count] = buffer_copy;
while( *ptr )
if( ( *ptr == '#' ) || ( *ptr == '\n' ) )
*ptr++ = '\0', tokens[++token_count] = ptr;
else
++ptr;
size_t index;
for( index = 0; index < token_count; ++index )
if( !strcmp( tokens[index], "member" ) )
printf( "%d: %s | %s", index, tokens[index], buffer );
}
fclose( fin );
return 0;
}
If you go with fixed position (always 3rd (0 indexed)), you can just scan and check:
int is_member( const char * buffer )
{
if( !buffer )
return 0;
size_t index;
const char * ptr = buffer;
for( index = 0; index < 3; ++index, ++ptr )
if( !( ptr = strchr( ptr, '#' ) ) )
return 0;
return !strncmp( ptr, "member", 6 ) && ( ( *( ptr + 7 ) == 0 ) || ( *( ptr + 7 ) == '#' ) || ( *( ptr + 7 ) == '\n' ) );
}
int main( int argc, char ** argv )
{
FILE * fin = fopen( argv[1], "rt" );
if( !fin )
return 1;
char buffer[1000];
while( fgets( buffer, 1000, fin ) )
if( is_member( buffer ) )
printf( "%s", buffer );
fclose( fin );
return 0;
}
Or if the position is not known, then you can find each token on the fly. This takes no significant additional memory (a couple pointers) and does not modify your buffer:
int is_member( const char * buffer, const char * delimiters )
{
size_t index;
const char * ptr = buffer, * eptr = buffer;
for( ; eptr; ptr = eptr + 1 )
// If the next delimiter is found and it is 6 characters away or not found, and the substring matches 'member', return 1.
if( ( !( eptr = strpbrk( ptr, delimiters ) ) || ( eptr - ptr == 6 ) ) &&
!strncmp( ptr, "member", 6 ) )
return 1;
return 0;
}
int main( int argc, char ** argv )
{
FILE * fin = fopen( argv[1], "rt" );
if( !fin )
return 1;
char buffer[1000];
while( fgets( buffer, 1000, fin ) )
if( is_member( buffer, "#\n" ) )
printf( "%s", buffer );
fclose( fin );
return 0;
}

Answer 3

I did it it without using file * since I have the buffer already. It is working. thanks.
char buffer_copy[1000];
strcpy( buffer_copy, buffer );
char * tokens[1000];
size_t token_count = 0;
char * ptr = tokens[token_count] = buffer_copy;
while( *ptr )
if( ( *ptr == '#' ) || ( *ptr == '\n' ) )
*ptr++ = '\0', tokens[++token_count] = ptr;
else
++ptr;
size_t index;
for( index = 0; index < token_count; ++index )
if( !strcmp( tokens[index], "member" ) )
printf( "%d: %s | %s", index, tokens[index], buffer );