String Manipulation Functions in C

C provides built-in library functions to work with strings — declared in <string.h>. These let you copy, concatenate, compare, measure, and reverse strings without writing the logic yourself.

#include <string.h>

1. `strlen()` — Get the Length

Returns the number of characters in a string, excluding the null terminator '\0'.

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

int main() {
    char name[20] = "Vishal";
    int len = strlen(name);
    printf("Length = %d", len);   // Output: 6
    return 0;
}

2. `strcpy()` — Copy a String

Copies the content of one string into another. The destination must be large enough.

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

int main() {
    char str1[20] = "Hello";
    char str2[20];
    strcpy(str2, str1);
    printf("Copied: %s", str2);   // Output: Hello
    return 0;
}

3. `strcat()` — Concatenate Strings

Appends one string to the end of another. The destination must have enough space.

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

int main() {
    char str1[30] = "Hello ";
    char str2[10] = "World!";
    strcat(str1, str2);
    printf("%s", str1);   // Output: Hello World!
    return 0;
}

4. `strcmp()` — Compare Strings

Compares two strings character by character:

Returns 0 if both strings are equal
Returns > 0 if the first string is greater
Returns < 0 if the second string is greater

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

int main() {
    char str1[20] = "abc";
    char str2[20] = "abd";
    int result = strcmp(str1, str2);
    if (result == 0)
        printf("Strings are equal");
    else
        printf("Strings are not equal");
    return 0;
}
// Output: Strings are not equal

5. `strrev()` — Reverse a String

Reverses the string in place. Available in Turbo C / MinGW compilers — not in all compilers (not part of the C standard).

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

int main() {
    char str[20] = "Future";
    printf("Reversed: %s", strrev(str));
    return 0;
}
// Output: Reversed: erutuF

For portability, write your own reverse:

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

void reverseStr(char str[]) {
    int n = strlen(str);
    for (int i = 0; i < n / 2; i++) {
        char temp = str[i];
        str[i] = str[n - 1 - i];
        str[n - 1 - i] = temp;
    }
}

Quick Reference

All functions below need #include <string.h>.

Function	Description
`strlen(s)`	Length of string (excludes `'\0'`)
`strcpy(d, s)`	Copy `s` into `d`
`strcat(d, s)`	Append `s` to end of `d`
`strcmp(s1, s2)`	Compare two strings
`strrev(s)`	Reverse string (compiler-specific)
`strupr(s)`	Convert to uppercase (Turbo C)
`strlwr(s)`	Convert to lowercase (Turbo C)

Fundamentals

Functions

Array

String

Structure

Union

Pointer

File Handling

Preprocessor

String Manipulation Functions

String Manipulation Functions in C

1. `strlen()` — Get the Length

2. `strcpy()` — Copy a String

3. `strcat()` — Concatenate Strings

4. `strcmp()` — Compare Strings

5. `strrev()` — Reverse a String

Quick Reference

​String Manipulation Functions in C

​1. strlen() — Get the Length

​2. strcpy() — Copy a String

​3. strcat() — Concatenate Strings

​4. strcmp() — Compare Strings

​5. strrev() — Reverse a String

​Quick Reference

String Manipulation Functions in C

1. `strlen()` — Get the Length

2. `strcpy()` — Copy a String

3. `strcat()` — Concatenate Strings

4. `strcmp()` — Compare Strings

5. `strrev()` — Reverse a String

Quick Reference