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String functions

Posted By: Freya Brown     Category: C Programming     Views: 5359

Program of string functions.

Code for String functions in C Programming

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <alloc.h>

int search ( char *, char ) ;
int isequals ( char *, char * ) ;
int issmaller ( char *, char * ) ;
int isgreater ( char *, char * ) ;
char * getsub ( char *, int, int ) ;
char * leftsub ( char *, int n ) ;
char * rightsub ( char *, int n ) ;
void upper ( char * ) ;
void lower ( char * ) ;
void reverse ( char * ) ;
int replace ( char *, char, char ) ;
int setat ( char *, char, int ) ;

void main( )
{
    char s1[ ] = "Hello" ;
    char s2[ ] = "Hello World" ;
    char s3[ ] = "Four hundred thirty two" ;
    char ch, *s ;
    int i ;

    clrscr( ) ;

    printf ( "\nString s1: %s", s1 ) ;

    /* check for the first occurrence of a character */
printf ( "\nEnter character to search: " ) ; scanf ( "%c", &ch ) ; i = search ( s1, ch ) ; if ( i != -1 ) printf ( "The first occurrence of character %c is found at index no. %d\n", ch, i ) ; else printf ( "Character %c is not present in the list.\n", ch ) ; printf ( "\nString s2: %s", s2 ) ; /* compares two strings s1 and s2 */
i = isequals ( s1, s2 ) ; if ( i == 1 ) printf ( "\nStrings s1 and s2 are identical" ) ; else printf ( "\nStrings s1 and s2 are not identical") ; i = issmaller ( s1, s2 ) ; if ( i == 1 ) printf ( "\nString s1 is smaller than string s2" ) ; else printf ( "\nString s1 is not smaller than string s2" ) ; i = isgreater ( s1, s2 ) ; if ( i == 1 ) printf ( "\nString s1 is greater than string s2\n" ) ; else printf ( "\nString s1 is not greater than string s2\n" ) ; /* extract characters at given position */
printf ( "\nString s3: %s", s3 ) ; s = getsub ( s3, 5, 7 ) ; printf ( "\nSub string: %s", s ) ; free ( s ) ; /* extract leftmost n characters */
s = leftsub ( s3, 4 ) ; printf ( "\nLeft sub string: %s", s ) ; free ( s ) ; /* extract rightmost n characters */
s = rightsub ( s3, 3 ) ; printf ( "\nRight sub string: %s", s ) ; free ( s ) ; /* convert string to uppercase */
upper ( s3 ) ; printf ( "\nString in upper case: %s", s3 ) ; /* convert string to lowercase */
lower ( s3 ) ; printf ( "\nString in lower case: %s", s3 ) ; /* reverse the given string */
reverse ( s3 ) ; printf ( "\nReversed string: %s", s3 ) ; /* replace first occurrence of one char with new one */
replace ( s1, 'H' , 'M' ) ; printf ( "\nString s1: %s", s1 ) ; /* sets a char at a given position */
i = setat ( s1, 'M', 3 ) ; if ( i ) printf ( "\nString s1: %s", s1 ) ; else printf ( "\nInvalid position." ) ; getch( ) ; } /* check for the first occurrence of a character */
int search ( char *str, char ch ) { int i = 0 ; while ( *str ) { if ( *str == ch ) return i ; str++ ; i++ ; } return -1 ; } /* checks whether two strings are equal */
int isequals ( char *s, char *t ) { while ( *s || *t ) { if ( *s != *t ) return 0 ; s++ ; t++ ; } return 1 ; } /* checks whether first string is less than second */
int issmaller ( char *s, char *t ) { while ( *t ) { if ( *s != *t ) { if ( *s < *t ) return 1 ; elsereturn 0 ; } t++ ; s++ ; } return 0 ; } /* checks whether first string is greater than second */
int isgreater ( char *s, char *t ) { while ( *s ) { if ( *s != *t ) { if ( *s > *t ) return 1 ; elsereturn 0 ; } s++ ; t++ ; } return 0 ; } /* extracts the character at given position */
char * getsub ( char *str, int spos, int n ) { char *s = str + spos ; char *t = ( char * ) malloc ( n + 1 ) ; int i = 0 ; while ( i < n ) { t[i] = *s ; s++ ; i++ ; } t[i] = '\0' ; return t ; } /* extracts leftmost n characters from the string */
char * leftsub ( char *s, int n ) { char *t = ( char * ) malloc ( n + 1 ) ; int i = 0 ; while ( i < n ) { t[i] = *s ; s++ ; i++ ; } t[i] = '\0' ; return t ; } /* extracts rightmost n characters from the string */
char * rightsub ( char *str, int n ) { char *t = ( char * ) malloc ( n + 1 ) ; int l = strlen ( str ) ; char *s = str + ( l - n ) ; int i = 0 ; while ( i < n ) { t[i] = *s ; s++ ; i++ ; } t[i] = '\0' ; return t ; } /* converts string to uppercase */
void upper ( char *s ) { while ( *s ) { if ( *s >= 97 && *s <= 123 ) *s -= 32 ; s++ ; } } /* converts string to lowercase */
void lower ( char *s ) { while ( *s ) { if ( *s >= 65 && *s <= 91 ) *s += 32 ; s++ ; } } /* reverses a string */
void reverse ( char *str ) { int l = strlen ( str ) ; char ch, *t = ( str + l - 1 ) ; int i = 0 ; while ( i < l / 2 ) { ch = *str ; *str = *t ; *t = ch ; str++ ; t-- ; i++ ; } } /* replaces the first occurrence of char with new char */
int replace ( char *str, char oldch, char newch ) { while ( *str ) { if ( *str == oldch ) { *str = newch ; return 1 ; } str++ ; } return 0 ; } /* sets a char at a given position */
int setat ( char *str, char ch, int i ) { if ( i < 0 || strlen ( str ) < i ) return 0 ; * ( str + i ) = ch ; return 1 ; }
  
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Freya Brown
Freya Brown author of String functions is from London, United Kingdom.
 
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