Standard Library String Handling Functions:
There
are a large number of library functions available in C that allows to operate
strings. Using these operations, the strings can be compared, copied and
concatenated (i.e. combine one after another). Some of commonly available
library functions in C are listed below. They all are included in a header file
string.h.
1. strlen ( ): This function returns the
number of characters in a string, not counting the terminating NULL character.
For example:
int a;
char name[ ]= “ABC”;
a = strlen (name);
will store 3 in a as the length of the string.
2.
strcpy ( ): The strcpy function works
like a string-assignment operator. It takes the form:
strcpy
(string1,string2);
and assigns the contents of
string2 to string1. string2 may be a character array variable or
a string constant. For example, the
statement
strcpy (city,”DELHI”);
will assign the string “DELHI” to the variable city.
Similarly the statement
strcpy (city1,city2);
will assign the contents of the string variable city2
to the variable city1. The size of the array city1 should be large enough to
receive the contents of city2..
3.
strcat ( ): The strcat function joins two strings together. It
takes the following form:
string1 and string2
are character arrays. When the function strcat is executed, string2 is appended
to string1. It does so by removing the null character at the string1 and
placing string2 from there. The string at string2 remains unchanged. For
example, consider the following strings:
4.
strcmp ( ) function:
The strcmp function compares two strings identified by the
arguments and has a value 0 if they are equal. If they are not, it has the
numeric difference between the first non matching characters in the strings. It
takes the form:
string1 and string2 may be string variables or
string constants. Examples are:
strcmp
(name1, name2);
strcmp
(name1, “JHON”);
strcmp
(“ROM”, “RAM”);
Our major concern is to determine wheather
the strings are equal; if not, which is alphabetically above. The mismatch is
rarely important. For example, the statement
strcmp (“their”, “there”);
will return a value of -9 which is the
numerical difference between ASCII “i” and ASCII “r”. That is “i” minus “r” in
ASCII code is -9. If the value is negative, string1 is alphabetically above
string2.
5.
strstr ( )
function:
It is a two- parameter function that can be
used to locate s sub-string in a string. This takes the forms:
strstr (s1,s2);
strstr (s1,
“ABC”);
The function strstr searches the string s1 to
see whether the string s2 is contained in s1. If yes, the function returns the
position of the first occurrence of the sub- string. Otherwise, it returns a
NULL pointer, For example:
if
(strstr (s1,s2 == NULL)
printf(“substring
is not found”);
else
printf(“s2
is a sub- string of s1);
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