delete the file contents

Hi All,

I would like to delete the specific lines in a file programmatically, is there any way I can do that? Similar to the one we do it in notepad i.e. as soon as we delete a line the line below the deleted line would occupy the current position.

Thanks in advance

Open the file. Read the contents. Remove what you want. Save the new version. Just like how notepad works.


Quzah.

Quote:

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Originally Posted by jayfriend

Hi All,

I would like to delete the specific lines in a file programmatically, is there any way I can do that? Similar to the one we do it in notepad i.e. as soon as we delete a line the line below the deleted line would occupy the current position.

Thanks in advance

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Text files may have a couple of unseen char's at the end of each line - Carriage Return (CR) and Line Feed (LF). This is a very old convention that is still used in Windows and DOS text files.

When your program deletes the unwanted line, check to be sure it is also deleting the CR/LF combination of char's which will exist wherever a hard return is located in the file. "Soft" returns are handled by the displaying program, and do not require a CR/LF combo. For example:

This is a line with a hard return at the end. CR/LF

This line is very long, exceeding the line length of the display program, and so it won't have a hard return located at the end of the first line, but will have one at the end of the second line.

I don't have my ascii chart handy, but CR and LF's are ascii 10 and 12, iirc.

Adak

Quote:

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Originally Posted by quzah

Open the file. Read the contents. Remove what you want. Save the new version. Just like how notepad works.


Quzah.

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I am looking for a function or system call with which we can delete the file contents.
Please let me know your suggestions on this.

Thanks in advance.

Due to the nature of C being available everywhere, and the fact that different systems have different conventions for text files, there can't possibly be a standard function or a reliable "system call," since your system could be anything as far as I know.

Make a function that does what you need. It'll be less of a hassle.

fopen(file, "w"); //never used C file io but from what I understand this opens a file to write and truncates it.

Hi Citizen,

Quote:

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Originally Posted by citizen

Due to the nature of C being available everywhere, and the fact that different systems have different conventions for text files, there can't possibly be a standard function or a reliable "system call," since your system could be anything as far as I know.

Make a function that does what you need. It'll be less of a hassle.

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Could you please help me write the function which will delete the contents of a file.

Thanks in advance.

Quote:

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Originally Posted by c99

7.19.4.1 The remove function
Synopsis
1 #include <stdio.h>
int remove(const char *filename);
Description
2 The remove function causes the file whose name is the string pointed to by filename
to be no longer accessible by that name. A subsequent attempt to open that file using that
name will fail, unless it is created anew. If the file is open, the behavior of the remove
function is implementation-defined.
Returns
3 The remove function returns zero if the operation succeeds, nonzero if it fails.

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It also exists in C89.
It's in stdio.h

Quote:
Originally Posted by c99
7.19.4.1 The remove function

Quote:

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Synopsis
1 #include <stdio.h>
int remove(const char *filename);
Description
2 The remove function causes the file whose name is the string pointed to by filename
to be no longer accessible by that name. A subsequent attempt to open that file using that
name will fail, unless it is created anew. If the file is open, the behavior of the remove
function is implementation-defined.
Returns
3 The remove function returns zero if the operation succeeds, nonzero if it fails.

It also exists in C89.
It's in stdio.h

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But how do I truncate the file? How I delete the selected lines of a file?

Thanks in advance.

You've already been told how to do it. One more time.

Open.
Read.
Edit.
Write.
Close.


Quzah.

Create a buffer of the file. Compress the buffer. Delete the file (remove). Write the buffer to a file.

FILE:"This is an Example."

Code:

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#include <stdio.h>
#include <stdlib.h> // for malloc/free
#include "yourfunctions.h"
int main(void)
{
        char *mybigbuffer;
        mybigbuffer = malloc(BIGBUFFERSIZE); // defined in yourfunctions.h
        if (mybigbuffer == NULL){
                crapout();
                return -1;
        }
        doreadme("FILE", mybigbuffer);
        remove("FILE");  // BTW, this is redundant.
        doremovetext(mybigbuffer, "is an Ex");
        dowriteme("FILE", mybigbuffer);
        free(mybigbuffer);
        return 0;
}

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FILE:"This ample."