deleting a string from a particular position in a file

Question

I want to delete a string from a particular position in the file. Is thre a function to do that? Can I delete last line of a file through a function?

What kind of string? You gotta specify.

Tyler Crompton
– Tyler Crompton

2011-03-31 06:52:11 +00:00
Commented Mar 31, 2011 at 6:52 — Tyler Crompton
– Tyler Crompton, Commented Mar 31, 2011 at 6:52

N 1.1 · Accepted Answer · 2011-03-31 07:02:13Z

2

You have two option

To read whole file, remove what you need and write it back
If the file is big, read file sequentially, remove given part, and move content after that forward

edited Mar 31, 2011 at 7:02

N 1.1

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answered Mar 31, 2011 at 6:53

Arsen Mkrtchyan

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2 Comments

Shweta Over a year ago

"move content after that forward" How?

Arsen Mkrtchyan Over a year ago

By rewriting part after removed content

Shamim Hafiz - MSFT · Accepted Answer · 2011-03-31 06:53:59Z

2

No there is no such function that will let you do this directly on a file.

You should load up the file content in memory and modify there and write back to file.

answered Mar 31, 2011 at 6:53

Shamim Hafiz - MSFT

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Comments

Bwmat · Accepted Answer · 2011-03-31 08:02:33Z

1

I don't feel like looking up all the io functions, so here's pseudo-c on how to implement option 2 of ArsenMkrt's answer

char buffer[N]; // N >= 1
int str_start_pos = starting position of the string to remove
int str_end_pos = ending position of the string to remove
int file_size = the size of the file in bytes
int copy_to = str_start_pos 
int copy_from = str_end_pos + 1

while(copy_from < file_size){
    set_file_pos(file, copy_from)
    int bytes_read = read(buffer, N, file)
    copy_from += bytes_read
    set_file_pos(file, copy_to)
    write(buffer, file, bytes_read)
    copy_to += bytes_read
}
truncate_file(file,file_size - (str_end_pos - str_start_pos + 1))

something to that effect

answered Mar 31, 2011 at 8:02

Bwmat

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