File Descriptor on Amit Agarwal Linux Blog

symlinks -delete all invalid soft links in Linux/Fedora

Tue, 12 Jun 2012 01:05:34 +0000

First of all, install symlinks if it is not installed :

sudo yum install symlinks

and here is the description:

Description : The symlinks utility performs maintenance on symbolic links.

Symlinks checks for symlink problems, including dangling symlinks

which point to nonexistent files. Symlinks can also automatically

convert absolute symlinks to relative symlinks.

Install the symlinks package if you need a program for maintaining

symlinks on your system.

and the help for the same:

faster bash operations on files with File Descriptors.

Sat, 11 Jun 2011 02:11:53 +0000

I was writing a bash script that would do some operations and read and write to file. Seems that that was pretty simple with

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      while read line<br /> <br /> do<br /> <br /> done<file
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and then use redirection operations like “>” and “»” to write to file. Done with the script pretty fast. So far so good, when I went for real life tests, no one was interested in using it, why? Simple, it was simply taking too long. The file was reading about 10K lines and writing about 50 lines and was taking about more than 10 minutes.

tee to a file descriptor

Fri, 13 Aug 2010 03:22:44 +0000

tee to a file descriptor

`1`	`$ tee >(cat – >&2)`

the tee command does fine with file names, but not so much with file descriptors, such as &2. This uses process redirection to tee to the specified descriptor.

In the sample output, it’s being used to tee to stderr, which is connected with the terminal, and to wc -l, which is also outputting to the terminal. The result is the output of bash –version followed by the linecount

coproc help - a new feature in bash

Mon, 10 May 2010 15:07:45 +0000

: Image via Wikipedia

In the <a class="zem_slink freebase/en/bash" title="Bash" rel="homepage" href="http://tiswww.case.edu/php/chet/bash/bashtop.html">bash version 4.0, there is a new concept called coproc. This is very useful for some of the daily tasks.

co-<a class="zem_slink freebase/guid/9202a8c04000641f800000000005a409" title="Process (computing)" rel="wikipedia" href="http://en.wikipedia.org/wiki/Process_%28computing%29">process starts a process in the background, optionally with a NAME, with which other processes can communicate. This can be a very <a class="zem_slink freebase/en/substitute_good" title="Substitute good" rel="wikipedia" href="http://en.wikipedia.org/wiki/Substitute_good">good substitution for <a class="zem_slink freebase/guid/9202a8c04000641f800000000048fac5" title="Pipeline (Unix)" rel="wikipedia" href="http://en.wikipedia.org/wiki/Pipeline_%28Unix%29">pipes in lots of cases. You can learn more about coproc in the link below:

prepend to a file with sponge from moreutils

Tue, 16 Mar 2010 02:25:42 +0000

<a href="http://bashcurescancer.com/prepend-to-a-file-with-sponge-from-moreutils.html">A few weeks I wrote about a tool, which helps you easily prepend to a file. I submitted prepend to moreutils and Joey was kind enough to point out this could be done with `sponge’.? sponge reads standard input and when done, writes it to a file:
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