How to Replace a Substring in String in C - Step by Step Examples

How to Replace a Substring in String in C ?

Answer

To replace a substring in a string in C, you can create a function that finds the substring and replaces it with another substring. This involves using functions from the string.h library.

✐ Examples

1 Replace Substring in a String

In this example,

We include the necessary header string.h for string handling functions.
We create a function named replaceSubstring to replace a substring.
Inside the function, we find the position of the substring to be replaced using strstr.
If the substring is found, we copy the part before the substring, add the new substring, and then add the part after the substring to the result.
We return the modified string.
We call the replaceSubstring function with the original string, the substring to be replaced, and the new substring.
Finally, we print the modified string to the standard output.

C Program

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

void replaceSubstring(char *str, const char *old_sub, const char *new_sub) {
    char buffer[100];
    char *pos;

    pos = strstr(str, old_sub);
    if (pos != NULL) {
        // Copy the part before the old substring
        strncpy(buffer, str, pos - str);
        buffer[pos - str] = '\0';

        // Add the new substring
        strcat(buffer, new_sub);

        // Add the part after the old substring
        strcat(buffer, pos + strlen(old_sub));

        // Copy the result back to the original string
        strcpy(str, buffer);
    }
}

int main() {
    char str[100] = "Hello World";
    const char *old_sub = "World";
    const char *new_sub = "Everyone";

    replaceSubstring(str, old_sub, new_sub);
    printf("Modified string: %s\n", str);

    return 0;
}

Output

Modified string: Hello Everyone

2 Replace Another Substring in a Different String

In this example,

We include the necessary header string.h for string handling functions.
We create a function named replaceSubstring to replace a substring.
Inside the function, we find the position of the substring to be replaced using strstr.
If the substring is found, we copy the part before the substring, add the new substring, and then add the part after the substring to the result.
We return the modified string.
We call the replaceSubstring function with the original string, the substring to be replaced, and the new substring.
Finally, we print the modified string to the standard output.

C Program

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

void replaceSubstring(char *str, const char *old_sub, const char *new_sub) {
    char buffer[100];
    char *pos;

    pos = strstr(str, old_sub);
    if (pos != NULL) {
        // Copy the part before the old substring
        strncpy(buffer, str, pos - str);
        buffer[pos - str] = '\0';

        // Add the new substring
        strcat(buffer, new_sub);

        // Add the part after the old substring
        strcat(buffer, pos + strlen(old_sub));

        // Copy the result back to the original string
        strcpy(str, buffer);
    }
}

int main() {
    char str[100] = "Good Morning";
    const char *old_sub = "Morning";
    const char *new_sub = "Evening";

    replaceSubstring(str, old_sub, new_sub);
    printf("Modified string: %s\n", str);

    return 0;
}

Output

Modified string: Good Evening

Summary

In this tutorial, we learned How to Replace a Substring in String in C language with well detailed examples.

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How to Replace a Substring in String in C - Step by Step Examples

How to Replace a Substring in String in C ?

Answer

✐ Examples

1 Replace Substring in a String

C Program

Output

2 Replace Another Substring in a Different String

C Program

Output

Summary

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