Lära Building Simple String Utilities | Practical String Processing

Definition

Definition: A string utility is a small, reusable function or program that performs a specific task involving the manipulation, analysis, or validation of strings. The purpose of a string utility is to simplify common operations on text, such as searching, counting, or formatting, making it easier to process and manage string data in your programs.

You often need to process strings in C for practical tasks. Common string utility tasks include counting the number of words in a sentence, checking if user input contains only valid characters, or validating that a string matches a required pattern. These utilities help ensure data is clean, formatted correctly, and ready for further processing. For instance, you might want to count words in a sentence to give feedback to a user, or check that a phone number contains only digits before saving it.

main.c


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#include <stdio.h>
#include <ctype.h>

int count_words(const char *str) {
    int count = 0;
    int in_word = 0;
    while (*str) {
        if (!isspace((unsigned char)*str)) {
            if (!in_word) {
                count++;
                in_word = 1;
            }
        } else {
            in_word = 0;
        }
        str++;
    }
    return count;
}

int main() {
    char text[100];

    printf("Enter a string: ");
    fgets(text, sizeof(text), stdin);

    int words = count_words(text);
    printf("Number of words: %d\n", words);

    return 0;
}

The logic for counting words in a string involves scanning each character and detecting transitions from whitespace to non-whitespace. The isspace function from ctype.h helps identify spaces, tabs, or newlines. Each time a non-space character follows a space, a new word is counted. The function keeps track of whether it is currently inside a word using the in_word flag. This approach works for most simple text inputs, making use of standard string and character handling functions.

main.c


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#include <stdio.h>
#include <ctype.h>

int is_all_digits(const char *str) {
    while (*str) {
        if (!isdigit((unsigned char)*str)) {
            return 0;
        }
        str++;
    }
    return 1;
}

int main() {
    char input[100];

    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);

    // Remove trailing newline if present
    char *newline = input;
    while (*newline) {
        if (*newline == '\n') {
            *newline = '\0';
            break;
        }
        newline++;
    }

    if (is_all_digits(input)) {
        printf("The string contains only digits.\n");
    } else {
        printf("The string contains non-digit characters.\n");
    }

    return 0;
}

You can extend these string utilities to perform other validation or processing tasks. For example, you might write a function to check if a string contains only alphabetic characters, or to search for a substring within another string. By combining standard library functions like strchr, strstr, or character tests from ctype.h, you can build a wide range of useful utilities tailored to your application's requirements.

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Definition

main.c


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#include <stdio.h>
#include <ctype.h>

int count_words(const char *str) {
    int count = 0;
    int in_word = 0;
    while (*str) {
        if (!isspace((unsigned char)*str)) {
            if (!in_word) {
                count++;
                in_word = 1;
            }
        } else {
            in_word = 0;
        }
        str++;
    }
    return count;
}

int main() {
    char text[100];

    printf("Enter a string: ");
    fgets(text, sizeof(text), stdin);

    int words = count_words(text);
    printf("Number of words: %d\n", words);

    return 0;
}

main.c


              1234567891011121314151617181920212223242526272829303132333435363738
            
#include <stdio.h>
#include <ctype.h>

int is_all_digits(const char *str) {
    while (*str) {
        if (!isdigit((unsigned char)*str)) {
            return 0;
        }
        str++;
    }
    return 1;
}

int main() {
    char input[100];

    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);

    // Remove trailing newline if present
    char *newline = input;
    while (*newline) {
        if (*newline == '\n') {
            *newline = '\0';
            break;
        }
        newline++;
    }

    if (is_all_digits(input)) {
        printf("The string contains only digits.\n");
    } else {
        printf("The string contains non-digit characters.\n");
    }

    return 0;
}

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Tack för dina kommentarer!

Avsnitt 5. Kapitel 3