CODEWITHSUNDEEP
cfilefile-iofile-handling
mujahid
mujahid

Reputation: 701

How do I clear the whole contents of a file in C?

I have a file with some of user1's data. I want to use the same file for user2 by clearing the content of the file.

My idea is that when a new user comes, data of the previous user should be clear and the same file should be ready for the new user.

Upvotes: 30

Views: 148909

Answers (6)

SHASHI BHUSAN
SHASHI BHUSAN

Reputation: 710

I prefer to use:-

system("echo "" > filename_with_complet_path");

Upvotes: 0

pietervanderstar
pietervanderstar

Reputation: 199

I am using:

fp=freopen(NULL,"w",fp);

Upvotes: 2

lost_in_the_source
lost_in_the_source

Reputation: 11237

fclose(fopen("file.txt", "w"));

Why this works:

write: Create an empty file for output operations. If a file with the same name already exists, its contents are discarded and the file is treated as a new empty file.

(quote from http://www.cplusplus.com/reference/cstdio/fopen/)

Upvotes: 18

garvitlnmiit
garvitlnmiit

Reputation: 77

There are two ways:

1. fd=open(filename,O_RDONLY | O_WRONLY | O_TRUNC);


2. [cat /dev/null > filename] for BASH. It can be directly used in c program using [system()] system call. 

   system("cat /dev/null > filename");

Upvotes: 6

binW
binW

Reputation: 13722

As @stefan said using fopen() with "w" mode will do the job for you. When you open a file with "w" flag it creates an empty file for writing. If a file with the same name already exists its contents are erased and the file is treated as an empty new file.

If the file is already open you can use freopen() function from stdio.h with "w" mode as it will first close the file and then reopen it for writing erasing whatever was in the file previously.

Upvotes: 57

stefan
stefan

Reputation: 2886

with fopen(filename, flag) just open it with flag= "w" or "wb" and it will be cleared

Upvotes: 19

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