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Q&A

How can I modify the code above to accept string as user input and use strcmp to compare with the contents of the text file & then delete that line?

+1
−3

I want to enter a string to compare with the text file, and if that word matches, then I want to delete that line containing that string.

How can I modify the code below, since the code below takes line number as input to delete a specific line.

Thank you.

#include <stdio.h>
    
int main()
{
    FILE *fileptr1, *fileptr2;
    char filename[40];
    char ch;
    int delete_line, temp = 1;

    printf("Enter file name: ");
    scanf("%s", filename);
    //open file in read mode
    fileptr1 = fopen(filename, "r");
    ch = getc(fileptr1);
    while (ch != EOF)
    {
        printf("%c", ch);
        ch = getc(fileptr1);
    }
    //rewind
    rewind(fileptr1);
    printf(" \n Enter line number of the line to be deleted:");
    scanf("%d", &delete_line);
    //open new file in write mode
    fileptr2 = fopen("replica.c", "w");
    ch = 'A';
    while (ch != EOF)
    {
        ch = getc(fileptr1);
        //except the line to be deleted
        if (temp != delete_line)
        {
            //copy all lines in file replica.c
            putc(ch, fileptr2);
        }
        if (ch == '\n')
        {
            temp++;
        }
    }
    fclose(fileptr1);
    fclose(fileptr2);
    remove(filename);
    //rename the file replica.c to original name
    rename("replica.c", filename);
    printf("\n The contents of file after being modified are as follows:\n");
    fileptr1 = fopen(filename, "r");
    ch = getc(fileptr1);
    while (ch != EOF)
    {
        printf("%c", ch);
        ch = getc(fileptr1);
    }
    fclose(fileptr1);
    return 0;
}

Example of contents in text file:

hello world up

one two three

User input: hello

Updated contents in text file:

one two three

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3 comment threads

ch needs to be int (1 comment)
Does it really need to be words (in the lexical sense)? (1 comment)
Why is your question quoted? (3 comments)

1 answer

+2
−1

Assuming you're actually looking for a substring of a line in the file and not a word (which would require, as @elgonzo indicated, figuring out how to deal with spacing and word boundaries in general), you should look up information about the function strstr.

But also, strstr wants to accept a string to search in, and you're currently reading your file one character at a time. Make your life easier and read up on fgets too.

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1 comment thread

Regarding the deletion of lines in a text file. (2 comments)

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