print every nth line

2011-03-01 2 min read Bash Linux

Some time back I was working with lot of data and wanted to analyze only the every 10 line sometimes and sometimes every 20th line. I had to keep doing these changes in vim or otherwise so finally I wrote a program to do this for me. If you need such a program then here it is:

  <td>
    <div class="text codecolorer">
      #!/bin/bash -<br /> #===============================================================================<br /> #<br /> #          FILE:  print_nth_line.sh<br /> #<br /> #         USAGE:  ./print_nth_line.sh<br /> #<br /> #   DESCRIPTION:  Print every nth line<br /> #<br /> #       OPTIONS:  ---<br /> #  REQUIREMENTS:  ---<br /> #          BUGS:  ---<br /> #         NOTES:  ---<br /> #        AUTHOR:   (),<br /> #       COMPANY:<br /> #       VERSION:  1.0<br /> #       CREATED:  12/08/2010 05:36:53 PM IST<br /> #      REVISION:  ---<br /> #===============================================================================<br /> <br /> if [ x"$1" == "x" ]<br /> then<br /> echo "Please provide the line numbers to print .. .ex 3 will print 3,6,9"<br /> exit -1;<br /> fi<br /> if [ x"$2" == "x" ]<br /> then<br /> echo "Please provide the filename"<br /> exit -2;<br /> fi<br /> awk 'temp++ { if ( temp % '$1' == 0) print $1};' $2
    </div>
  </td>
</tr>

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

/bash debugger

2011-02-27 5 min read Bash Linux

9.2. A bash Debugger

In this section we’ll develop a very basic debugger for bash.[10] Most debuggers have numerous sophisticated features that help a programmer in dissecting a program, but just about all of them include the ability to step through a running program, stop it at selected places, and examine the values of variables. These simple features are what we will concentrate on providing in our debugger. Specifically, we’ll provide the ability to:

some bash exercise for you

2011-02-15 1 min read Bash

Here is some teaser for you, can you figure out how this works:

  <td>
    <div class="text codecolorer">
      echo ls<br /> <br /> !!:1-$
    </div>
  </td>
</tr>

1
2
3

ovigia: #tips: #Bash Shell Scripts and Tutorials | BashShell.net (bashshell.net)
perl is faster than bash in some cases. (amit-agarwal.co.in)
bash math (amit-agarwal.co.in)

bash regular expressions

2011-02-06 1 min read Bash

Here are some quick links on bash regular expressions, pretty good links to bookmark, if you use, regular expressions in bash regularly. I especially like the tldp link at number 3.

http://www.linuxjournal.com/content/bash-regular-expressions
http://www.ibm.com/developerworks/library/l-bash.html
http://tldp.org/LDP/abs/html/parameter-substitution.html#VARMATCH
http://wellington.pm.org/archive/200005/codegen/index9.htm

Renaming a whole bunch of files at once, in bash (ask.metafilter.com)
bash math (amit-agarwal.co.in)
Efficiency of regular expressions (johndcook.com)
Autogenerate Regular Expressions with txt2re (readwriteweb.com)

bash mathematical calculators.

2011-01-25 3 min read Bash Fedora Learning Linux

To start with , the most simple and easy to use should be “bc”. but just for some guys who want to be more experimental, here are few more bash calulator programs. These are completely command line and thus you can completely integrate them in your shell script or use them in shell script to do some really crazy maths calculations.

  <td>
    <div class="text codecolorer">
      sudo yum install calc clac
    </div>
  </td>
</tr>

Lets start with installing these. Before we start, don’t blame and flame me if your favourite is not there in the list. If it is not, better is you drop me a comment or email, and I will see, if I can include it in the list above, but remember this is only for console based calculators.

shopt causes bash completion to stop working.

2011-01-25 1 min read Bash

Couple of days, I added some scripts to my bash startup and suddenly realized that bash completions stopped working. This is tricky situation in bash to figure out what went wrong. So, I set my foot down to make sure that I find out the culprit. Thus I started with method of elimination. So, I started with nothing in .bashrc and kept adding my stuff in batches, until the said feature was broken. Once that happened I started removing the added ones, one by one, until my completion started working again.

Find all the missing paths in the PATH variable in bash script

2011-01-20 1 min read Bash Fedora Learning

Here is a simple script that will list out all the paths in the PATH variable that do not exist.

  <td>
    <div class="text codecolorer">
      #!/bin/bash -<br /> #===============================================================================<br /> #<br /> #          FILE:  wrong_path.sh<br /> #<br /> #         USAGE:  ./wrong_path.sh<br /> #<br /> #   DESCRIPTION:  Show Directories in the PATH Which does NOT Exist<br /> #<br /> #       OPTIONS:  ---<br /> #  REQUIREMENTS:  ---<br /> #          BUGS:  ---<br /> #         NOTES:  ---<br /> #        AUTHOR:  Amit Agarwal (AKA), amit.agarwal@amit-agarwal.co.in<br /> #       COMPANY:  Individual<br /> #       VERSION:  1.0<br /> #       CREATED:  09/20/2009 09:15:48 AM IST<br /> #      REVISION:  ---<br /> #===============================================================================<br /> <br /> set -o nounset                              # Treat unset variables as an error<br /> <br /> (IFS=:;for p in $PATH; do test -d $p || echo $p; done)
    </div>
  </td>
</tr>

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

Older posts Newer posts

9.2. A bash Debugger

Related articles

Related articles