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Write a C program to delete a specified line from a text file?

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asked Jan 8, 2014 by smith Geek (15,340 points)

1 Answer

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In this program, user is asked for a filename he needs to change. User is also asked for the line number that is to be deleted. The filename is stored in 'filename'. The file is opened and all the data is transferred  to another file except that one line the user specifies to delete.

Program: Program to delete a specific line.

#include <stdio.h>

int main() {

FILE *fp1, *fp2;

//consider 40 character string to store filename

char filename[40];

char c;

int del_line, temp = 1;

//asks user for file name

printf("Enter file name: ");

//receives file name from user and stores in 'filename'

scanf("%s", filename);

//open file in read mode

fp1 = fopen(filename, "r");

c = getc(fp1);

//until the last character of file is obtained

while (c != EOF)

{

printf("%c", c);

//print current character and read next character

c = getc(fp1);

}

//rewind

rewind(fp1);

printf(" \n Enter line number of the line to be deleted:");

//accept number from user.

scanf("%d", &del_line);

//open new file in write mode

fp2 = fopen("copy.c", "w");

c = getc(fp1);

while (c != EOF) {

c = getc(fp1);

if (c == '\n')

temp++;

//except the line to be deleted

if (temp != del_line)

{

//copy all lines in file copy.c

putc(c, fp2);

}

}

//close both the files.

fclose(fp1);

fclose(fp2);

//remove original file

remove(filename);

//rename the file copy.c to original name

rename("copy.c", filename);

printf("\n The contents of file after being modified are as follows:\n");

fp1 = fopen(filename, "r");

c = getc(fp1);

while (c != EOF) {

printf("%c", c);

c = getc(fp1);

}

fclose(fp1);

return 0;

}

Output:

Enter file name:abc.txt

hi.

hello

how are you?

I am fine

hope the same

Enter line number of the line to be deleted:4

The contents of file after being modified are as follows:

hi.

hello

how are you?

hope the same

Explanation:

In this program, user is asked for a filename that needs to be modified. Entered file name is stored in a char array 'filename'. This file is opened in read mode using file pointer 'fp1'. Character 'c' is used to read characters from the file and print them to the output. User is asked for the line number in the file to be deleted. The file pointer is rewinded back and all the lines of the file except for the line to be deleted are copied into another file "copy.c". Now "copy.c" is renamed to the original filename. The original file is opened in read mode and the modified contents of the file are displayed on the screen.
answered Jan 8, 2014 by rajesh Guru (39,140 points)

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