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 FREEBSD
cat
CAT(1) BSD General Commands Manual CAT(1)NAME
cat -- concatenate and print files
SYNOPSIS
cat [-belnstuv] [file ...]
DESCRIPTION
The cat utility reads files sequentially, writing them to the standard output. The file operands are processed in command-line order. If
file is a single dash ('-') or absent, cat reads from the standard input. If file is a UNIX domain socket, cat connects to it and then reads
it until EOF. This complements the UNIX domain binding capability available in inetd(8).
The options are as follows:
-b Number the non-blank output lines, starting at 1.
-e Display non-printing characters (see the -v option), and display a dollar sign ('$') at the end of each line.
-l Set an exclusive advisory lock on the standard output file descriptor. This lock is set using fcntl(2) with the F_SETLKW command.
If the output file is already locked, cat will block until the lock is acquired.
-n Number the output lines, starting at 1.
-s Squeeze multiple adjacent empty lines, causing the output to be single spaced.
-t Display non-printing characters (see the -v option), and display tab characters as '^I'.
-u Disable output buffering.
-v Display non-printing characters so they are visible. Control characters print as '^X' for control-X; the delete character (octal
0177) prints as '^?'. Non-ASCII characters (with the high bit set) are printed as 'M-' (for meta) followed by the character for the
low 7 bits.
EXIT STATUS
The cat utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
The command:
cat file1
will print the contents of file1 to the standard output.
The command:
cat file1 file2 > file3
will sequentially print the contents of file1 and file2 to the file file3, truncating file3 if it already exists. See the manual page for
your shell (e.g., sh(1)) for more information on redirection.
The command:
cat file1 - file2 - file3
will print the contents of file1, print data it receives from the standard input until it receives an EOF ('^D') character, print the con-
tents of file2, read and output contents of the standard input again, then finally output the contents of file3. Note that if the standard
input referred to a file, the second dash on the command-line would have no effect, since the entire contents of the file would have already
been read and printed by cat when it encountered the first '-' operand.
SEE ALSO head(1), more(1), pr(1), sh(1), tail(1), vis(1), zcat(1), fcntl(2), setbuf(3)
Rob Pike, "UNIX Style, or cat -v Considered Harmful", USENIX Summer Conference Proceedings, 1983.
STANDARDS
The cat utility is compliant with the IEEE Std 1003.2-1992 (``POSIX.2'') specification.
The flags [-belnstv] are extensions to the specification.
HISTORY
A cat utility appeared in Version 1 AT&T UNIX. Dennis Ritchie designed and wrote the first man page. It appears to have been cat(1).
BUGS
Because of the shell language mechanism used to perform output redirection, the command ``cat file1 file2 > file1'' will cause the original
data in file1 to be destroyed!
The cat utility does not recognize multibyte characters when the -t or -v option is in effect.
BSD January 29, 2013 BSD