STATEMENT: Write the function strindex(s, t), which returns the position of the
rightmost occurence of t in s, or -1 if there is none.
PURPOSE: this program prints the index of the rightmost match on the line.
The match we have to find is a char array named pattern. We also print out
the number of matches we have found. We will take the input from
command-line.
PROBLEM: Segmentation Fault
The programe compiles fine but at run-time it segfaults :(
here is my solution which is a little modified version of the example
provided in the same section:
/* Exercise # 4.1 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
enum MAXSIZE { ARR_SIZE = 1000 };
int getline( char current_line[], int max );
int str_index( char current_line[], char search_for[] );
char pattern[] = "term";
int match_num;
int main( void )
{
char current_line[ARR_SIZE];
int matched_idx, idx;
idx = 0;
while( getline(current _line, ARR_SIZE) 0 )
{
if( (matched_idx = str_index(curre nt_line, pattern)) >= 0 )
{
printf("\n%d matches, \n%d is the last to match", match_num, matched_idx);
}
}
return 0;
}
/* takes a line as input and returns the length of the line */
int getline( char s[], int max )
{
int c, i;
for( i = 0; ( (c = getchar()) != EOF && (c != '\n') && (--max 0) ); ++i )
{
s[i] = c;
}
if( c == '\n' )
{
s[i++] = '\n';
}
s[i] = '\0';
return i;
}
/* search for a pattern in the line, will save every index position of
source string where the pattern starts to match. For string the index we
use an array of ints. we then return the last element of array which is the
index of the rightmost match. We also return the number of matches we have
found using an int match_num.
*/
int str_index( char s[], char p[] )
{
int i, j, k;
int idx, last_match;
int saved_pos[ARR_SIZE];
memset( saved_pos, '\0', sizeof( saved_pos ));
idx = 0;
match_num = 0;
for( i = 0; s[i] != '\0'; ++i )
{
for( k = 0, j = i; p[k] != '\0' ; ++k, ++j )
{
if( s[j] != p[k] )
{
break;
}
}
if( (k 0) && p[k] == '\0' )
{
saved_pos[idx] = i;
++match_num;
}
}
last_match = sizeof(saved_po s) - 2;
/* it checks whether we have any match or not. If we do not have any match
* then we have nothing in array */
if( saved_pos[0] )
{
return saved_pos[last_match];
}
else
{
return -1;
}
}
=========== OUTPUT =============
/home/arnuld/programs/C $ gcc -ansi -pedantic -Wall -Wextra 4-1.c
/home/arnuld/programs/C $ ./a.out
terminal
and no one
and this
term
and Xterminal
segmentation fault
/home/arnuld/programs/C $
rightmost occurence of t in s, or -1 if there is none.
PURPOSE: this program prints the index of the rightmost match on the line.
The match we have to find is a char array named pattern. We also print out
the number of matches we have found. We will take the input from
command-line.
PROBLEM: Segmentation Fault
The programe compiles fine but at run-time it segfaults :(
here is my solution which is a little modified version of the example
provided in the same section:
/* Exercise # 4.1 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
enum MAXSIZE { ARR_SIZE = 1000 };
int getline( char current_line[], int max );
int str_index( char current_line[], char search_for[] );
char pattern[] = "term";
int match_num;
int main( void )
{
char current_line[ARR_SIZE];
int matched_idx, idx;
idx = 0;
while( getline(current _line, ARR_SIZE) 0 )
{
if( (matched_idx = str_index(curre nt_line, pattern)) >= 0 )
{
printf("\n%d matches, \n%d is the last to match", match_num, matched_idx);
}
}
return 0;
}
/* takes a line as input and returns the length of the line */
int getline( char s[], int max )
{
int c, i;
for( i = 0; ( (c = getchar()) != EOF && (c != '\n') && (--max 0) ); ++i )
{
s[i] = c;
}
if( c == '\n' )
{
s[i++] = '\n';
}
s[i] = '\0';
return i;
}
/* search for a pattern in the line, will save every index position of
source string where the pattern starts to match. For string the index we
use an array of ints. we then return the last element of array which is the
index of the rightmost match. We also return the number of matches we have
found using an int match_num.
*/
int str_index( char s[], char p[] )
{
int i, j, k;
int idx, last_match;
int saved_pos[ARR_SIZE];
memset( saved_pos, '\0', sizeof( saved_pos ));
idx = 0;
match_num = 0;
for( i = 0; s[i] != '\0'; ++i )
{
for( k = 0, j = i; p[k] != '\0' ; ++k, ++j )
{
if( s[j] != p[k] )
{
break;
}
}
if( (k 0) && p[k] == '\0' )
{
saved_pos[idx] = i;
++match_num;
}
}
last_match = sizeof(saved_po s) - 2;
/* it checks whether we have any match or not. If we do not have any match
* then we have nothing in array */
if( saved_pos[0] )
{
return saved_pos[last_match];
}
else
{
return -1;
}
}
=========== OUTPUT =============
/home/arnuld/programs/C $ gcc -ansi -pedantic -Wall -Wextra 4-1.c
/home/arnuld/programs/C $ ./a.out
terminal
and no one
and this
term
and Xterminal
segmentation fault
/home/arnuld/programs/C $
Comment