String Functions In C

char *strcpy(dest, src)
register char *dest, *src;
{
char *sav;

sav = dest;
while (*dest++ = *src++)
;
return sav;
}

char *strncpy(dest, src, len)
register char *dest, *src;
{
char *sav;

sav = dest;
while (len--) {
if ((*dest++ = *src++) == 0) {
while (len--)
*dest++ = 0;
break;
}
}
return sav;
}

char *strcat(dest, src)
register char *dest, *src;
{
char *sav;

sav = dest;
while (*dest)
++dest;
while (*dest++ = *src++)
;
return sav;
}

char *strncat(dest, src, len)
register char *dest, *src;
{
char *sav;

sav = dest;
while (*dest)
++dest;
do {
if (len-- == 0) {
*dest = 0;
break;
}
} while (*dest++ = *src++);
return sav;
}

strcmp(a, b)
register char *a, *b;
{
int i;

while ((i = *a - *b++) == 0 && *a++)
;
return i;
}

strncmp(a, b, len)
register char *a, *b;
{
int i = 0;

while (len-- && (i = *a - *b++) == 0 && *a++)
;
return i;
}

strlen(str)
register char *str;
{
register int len = 0;

while (*str++)
++len;
return len;
}

char *index(str, c)
register char *str; register int c;
{
while (*str) {
if (*str == c)
return str;
++str;
}
return (char *)0;
}

char *rindex(str, c)
register char *str; int c;
{
register char *cp;

for (cp = str ; *cp++ ; )
;
while (cp > str)
if (*--cp == c)
return cp;
return (char *)0;
}

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