By "clear" I take it you mean that you want to truncate the file to zero size.
In that case...
Opening a file for writing (as opposed to appending) means you will overwrite anything in aready in the file, so writing zero-length data to the file leaves you with a zero-length file, wiping out out everything that was there.
e.g.
Hello,
I want to clear or modify a line of a file. It is possible by
cat filename | sed '3d'
for example. But If I want "3" to be a variable?
I can't do sed '$var d'
Help me please
Thank you very much (1 Reply)
Hai,
I have a program which updates the result in a log file, as the program runs 24*7,the size of log file keeps on increasing.
Can you help me with a shell command which will clear the content of a log file in use.
1) I tried tail -10 logfile > logfile ( the content is not changed )
2) >... (10 Replies)
I have a log file on our system which fills up with lines that have been timestamped, as follows....
03/03/2008 10:56:06:815] (ERROR) balance: continuing session to genapp02 : 18500
03/03/2008 10:56:06:820] (ERROR) balance: continuing session to genapp02 : 18500
03/03/2008 10:56:07:003]... (2 Replies)
Hello,
I have a script which creates a certain text file.
Whenever I call it, I need to recreate this file, because I have no need in the previous content.
So I thought to remove the file every time I call the script, and that way I am sure that the previous content will not interrupt me.... (2 Replies)
How can i print the output of a perl script on a unix console and redirect the same in a log file under same directory simultaneously ?
Like in Shell script, we use tee, is there anything in Perl or any other option ? (2 Replies)
Hi,
I have a script which will use an input.txt file as an input file.
I am providing data to this input file in the script and once the script is executed, I want to clear all the contents of this file as during the second time use of this script, I'll be appending the data in this input... (5 Replies)
proc get_view_rel_str { } {
set cc_view :] end]]
puts $cc_view
set a
puts $a
set a end]]
puts $a
set a
puts $a
set a
puts $a
set a
puts $a
}
get_view_rel_str
this is a script in tcl with clearcase view (1 Reply)
Hi,
I have a file with 15 fields seperated by '|'. The requirement is to clear the last 5 characters of the 14th field. modifications should be done to the original file .
Can some one help me in sorting this out. (2 Replies)
Discussion started by: sureshk_85
2 Replies
LEARN ABOUT MOJAVE
truncate
TRUNCATE(2) BSD System Calls Manual TRUNCATE(2)NAME
ftruncate, truncate -- truncate or extend a file to a specified length
SYNOPSIS
#include <unistd.h>
int
ftruncate(int fildes, off_t length);
int
truncate(const char *path, off_t length);
DESCRIPTION
ftruncate() and truncate() cause the file named by path, or referenced by fildes, to be truncated (or extended) to length bytes in size. If
the file size exceeds length, any extra data is discarded. If the file size is smaller than length, the file is extended and filled with
zeros to the indicated length. The ftruncate() form requires the file to be open for writing.
Note: ftruncate() and truncate() do not modify the current file offset for any open file descriptions associated with the file.
RETURN VALUES
A value of 0 is returned if the call succeeds. If the call fails a -1 is returned, and the global variable errno specifies the error.
ERRORS
The ftruncate() system call will fail if:
[EBADF] fildes is not a valid descriptor open for writing.
[EFBIG] The file is a regular file and length is greater than the offset maximum established in the open file description associ-
ated with fildes.
[EINVAL] fildes references a socket, not a file.
[EINVAL] fildes is not open for writing.
[EROFS] The named file resides on a read-only file system.
The truncate() system call will fail if:
[EACCES] Search permission is denied for a component of the path prefix.
[EACCES] The named file is not writable by the user.
[EFAULT] Path points outside the process's allocated address space.
[EISDIR] The named file is a directory.
[ELOOP] Too many symbolic links are encountered in translating the pathname. This is taken to be indicative of a looping symbolic
link.
[ENAMETOOLONG] A component of a pathname exceeds {NAME_MAX} characters, or an entire path name exceeds {PATH_MAX} characters.
[ENOENT] The named file does not exist.
[ENOTDIR] A component of the path prefix is not a directory.
[EROFS] The named file resides on a read-only file system.
[ETXTBSY] The file is a pure procedure (shared text) file that is being executed.
The ftruncate() and truncate() system calls will fail if:
[EFBIG] The length argument was greater than the maximum file size.
[EINTR] A signal is caught during execution.
[EINVAL] The length argument is less than 0.
[EIO] An I/O error occurred while reading from or writing to a file system.
SEE ALSO open(2)BUGS
These calls should be generalized to allow ranges of bytes in a file to be discarded.
Use of truncate() to extend a file is not portable.
HISTORY
The truncate() and ftruncate() function calls appeared in 4.2BSD.
4.2 Berkeley Distribution June 4, 1993 4.2 Berkeley Distribution