C Exercises: Delete a specific line from a file
8. Delete Specific Line from File
Write a program in C to delete a specific line from a file.
Assume that the content of the file test.txt is : test line 1 test line 2 test line 3 test line 4
Sample Solution:
C Code:
#include <stdio.h>
#include <string.h>
#define MAX 256
int main()
{
int lno, ctr = 0;
char ch;
FILE *fptr1, *fptr2;
char fname[MAX];
char str[MAX], temp[] = "temp.txt";
printf("\n\n Delete a specific line from a file :\n");
printf("-----------------------------------------\n");
printf(" Input the file name to be opened : ");
scanf("%s",fname);
fptr1 = fopen(fname, "r");
if (!fptr1)
{
printf(" File not found or unable to open the input file!!\n");
return 0;
}
fptr2 = fopen(temp, "w"); // open the temporary file in write mode
if (!fptr2)
{
printf("Unable to open a temporary file to write!!\n");
fclose(fptr1);
return 0;
}
printf(" Input the line you want to remove : ");
scanf("%d", &lno);
lno++;
// copy all contents to the temporary file except the specific line
while (!feof(fptr1))
{
strcpy(str, "\0");
fgets(str, MAX, fptr1);
if (!feof(fptr1))
{
ctr++;
/* skip the line at given line number */
if (ctr != lno)
{
fprintf(fptr2, "%s", str);
}
}
}
fclose(fptr1);
fclose(fptr2);
remove(fname); // remove the original file
rename(temp, fname); // rename the temporary file to original name
/*------ Read the file ----------------*/
fptr1=fopen(fname,"r");
ch=fgetc(fptr1);
printf(" Now the content of the file %s is : \n",fname);
while(ch!=EOF)
{
printf("%c",ch);
ch=fgetc(fptr1);
}
fclose(fptr1);
/*------- End of reading ---------------*/
return 0;
}
Sample Output:
Delete a specific line from a file :
-----------------------------------------
Input the file name to be opened : test.txt
Input the line you want to remove : 2
Now the content of the file test.txt are :
test line 1
test line 3
test line 4
Flowchart:
For more Practice: Solve these Related Problems:
- Write a C program to delete multiple specified lines from a file based on user input.
- Write a C program to remove lines that contain a specific keyword from a file.
- Write a C program to delete the first and last lines from a file and then display the updated content.
- Write a C program to remove every even-numbered line from a file using file I/O operations.
Go to:
PREV : Count Words & Characters in File.
NEXT : Replace Specific Line in File.
C Programming Code Editor:
Have another way to solve this solution? Contribute your code (and comments) through Disqus.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.