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 FREEBSD
truncate
TRUNCATE(1) BSD General Commands Manual TRUNCATE(1)NAME
truncate -- truncate or extend the length of files
SYNOPSIS
truncate [-c] -s [+|-]size[K|k|M|m|G|g|T|t] file ...
truncate [-c] -r rfile file ...
DESCRIPTION
The truncate utility adjusts the length of each regular file given on the command-line.
The following options are available:
-c Do not create files if they do not exist. The truncate utility does not treat this as an error. No error messages are displayed and
the exit value is not affected.
-r rfile
Truncate or extend files to the length of the file rfile.
-s [+|-]size[K|k|M|m|G|g|T|t]
If the size argument is preceded by a plus sign (+), files will be extended by this number of bytes. If the size argument is pre-
ceded by a dash (-), file lengths will be reduced by no more than this number of bytes, to a minimum length of zero bytes. Other-
wise, the size argument specifies an absolute length to which all files should be extended or reduced as appropriate.
The size argument may be suffixed with one of K, M, G or T (either upper or lower case) to indicate a multiple of Kilobytes,
Megabytes, Gigabytes or Terabytes respectively.
Exactly one of the -r and -s options must be specified.
If a file is made smaller, its extra data is lost. If a file is made larger, it will be extended as if by writing bytes with the value zero.
If the file does not exist, it is created unless the -c option is specified.
Note that, while truncating a file causes space on disk to be freed, extending a file does not cause space to be allocated. To extend a file
and actually allocate the space, it is necessary to explicitly write data to it, using (for example) the shell's '>>' redirection syntax, or
dd(1).
EXIT STATUS
The truncate utility exits 0 on success, and >0 if an error occurs. If the operation fails for an argument, truncate will issue a diagnostic
and continue processing the remaining arguments.
SEE ALSO dd(1), touch(1), truncate(2)STANDARDS
The truncate utility conforms to no known standards.
HISTORY
The truncate utility first appeared in FreeBSD 4.2.
AUTHORS
The truncate utility was written by Sheldon Hearn <sheldonh@starjuice.net>.
BSD December 19, 2006 BSD