This isn't highly efficient (since it will copy the redundant bytes to the output file multiple time, doesn't try to align block sizes to disk block boundaries, uses small input block sizes if you have a large file that starts at a small [but non-zero] offset), but it seems to do what you want. You can make it considerably more complex to verify that the ranges of bytes specified by the input files don't leave any holes in the output file and to avoid copying duplicated data more than once. The checks for names that contain a "-" but are not just a string of digits followed by a "-" followed by a string of digits could be simplified with ksh and bash specific constructs. But the constructs used here should be portable to any shell that handles basic POSIX shell parameter expansion requirements correctly.
This is too simplistic to work if you want to process a file with a starting offset that is close to your process' maximum available address space. (In other words it probably won't work for terabyte sized files where the starting offset in one or more of your input files is relatively large.) But, it should give you a starting point for a more advanced script:
I use the Korn shell, but this script will work with any POSIX conforming shell without changing anything other than the first line in the script to specify your shell.
This User Gave Thanks to Don Cragun For This Post:
:mad: I did this the other day but one of my support personnel removed my history so i could call it back up to remeber the exact command since i am air-headed at times. I am trying to take a 30 MEG file off the system and drop it to tape then i want to make the file go back to being 0 bytes so... (1 Reply)
Hi all,
Does anybody know or guide me on how to remove the first N bytes and the last N bytes from a binary file? Is there any AWK or SED or any command that I can use to achieve this?
Your help is greatly appreciated!!
Best Regards,
Naveen. (1 Reply)
hi
My requirement is i have a file with some records like this
file name ::xyz
a=1
b=100,200
,300,400
,500,600
c=700,800
d=900
i want to change my file
a=1
b=100,200,300,400
c=700,800
d=900
if record starts with " , " that line should fallows the previous line.please give... (6 Replies)
What is the easiest way to inspect the bytes stored in a file?
Ideally, If my file was 10 bytes each of which had only the high bit set, I'd be able to browse for it and get output like this:
01 - 10000000
02 - 10000000
03 - 10000000
04 - 10000000
05 - 10000000
06 - 10000000
07 -... (7 Replies)
While running script I am getting an error like
Few lines in data are not being processed.
After googling it I came to know that adding such line would give some memory to it
ini_set("memory_limit","64M");
my input file size is 1 GB.
Is that memory limit is based on RAM we have on... (1 Reply)
Hi,
If I want to copy a 1024 byte data stream in to the target location in 3-bytes chunk, I guess I can use the following script.
dd bs=1024 count=3 if=/src of=/dest
But, I would like to know, how to do it via a C program. I have tried this with memcpy(), that did not help. (3 Replies)
Hello guys. I really hope someone will help me with this one..
So, I have to write this script who:
- creates a file home/student/vmdisk of 10 mb
- formats that file to ext3
- mounts that partition to /mnt/partition
- creates a file /mnt/partition/data. In this file, there will... (1 Reply)
hello,
suppose, entered input is of 1-40 bytes, i need it to be converted to 40 bytes exactly.
example: if i have entered my name anywhere between 1-40 i want it to be stored with 40 bytes exactly.
enter your name:
donald duck (this is of 11 bytes)
expected is as below - display 11... (3 Replies)
is there a better way to do this:
head -c 10000k /var/dump.log | head -c 6000k
unfortunately, the "-c" option is not available on sun solaris. so i'm looking at "dd". but i dont know how to use it to achieve the same exact goal as the above head command.
this needs to work on both solaris... (5 Replies)
Discussion started by: SkySmart
5 Replies
LEARN ABOUT REDHAT
seek
seek(n) Tcl Built-In Commands seek(n)
__________________________________________________________________________________________________________________________________________________NAME
seek - Change the access position for an open channel
SYNOPSIS
seek channelId offset ?origin?
_________________________________________________________________DESCRIPTION
Changes the current access position for channelId. ChannelId must be a channel identifier such as returned from a previous invocation of
open or socket. The offset and origin arguments specify the position at which the next read or write will occur for channelId. Offset must
be an integer (which may be negative) and origin must be one of the following:
start The new access position will be offset bytes from the start of the underlying file or device.
current The new access position will be offset bytes from the current access position; a negative offset moves the access position back-
wards in the underlying file or device.
end The new access position will be offset bytes from the end of the file or device. A negative offset places the access position
before the end of file, and a positive offset places the access position after the end of file.
The origin argument defaults to start.
The command flushes all buffered output for the channel before the command returns, even if the channel is in nonblocking mode. It also
discards any buffered and unread input. This command returns an empty string. An error occurs if this command is applied to channels
whose underlying file or device does not support seeking.
Note that offset values are byte offsets, not character offsets. Both seek and tell operate in terms of bytes, not characters, unlike |
read.
SEE ALSO
file(n), open(n), close(n), gets(n), tell(n)
KEYWORDS
access position, file, seek
Tcl 8.1 seek(n)