ShellCheck – check basic POSIX shell script errors

2015-08-03 1 min read Bash Fedora

Here is description of the tool:

Description : The goals of ShellCheck are:

To point out and clarify typical beginner’s syntax issues,
:   that causes a shell to give cryptic error messages.

To point out and clarify typical intermediate level semantic
:   problems, that causes a shell to behave strangely and
:   counter-intuitively.

To point out subtle caveats, corner cases and pitfalls, that may
:   cause an advanced user’s otherwise working script to fail under
:   future circumstances.

To install

evvsubst – substitute variables in text in shell

2015-07-09 1 min read Fedora Linux

First you need to install gettext, which by the way might be already installed, however you can install with

dnf install gettext

Details of the package:

Name        : gettext

Arch        : x86_64

Epoch       : 0

Version     : 0.19.4

Release     : 4.fc22

Size        : 4.6 M

Repo        : @System

Summary     : GNU libraries and utilities for producing multi-lingual messages

URL         : http://www.gnu.org/software/gettext/

License     : GPLv3+ and LGPLv2+

Description : The GNU gettext package provides a set of tools and documentation for

producing multi-lingual messages in programs. Tools include a set of

conventions about how programs should be written to support message

catalogs, a directory and file naming organization for the message

catalogs, a runtime library which supports the retrieval of translated

messages, and stand-alone programs for handling the translatable and

the already translated strings. Gettext provides an easy to use

library and tools for creating, using, and modifying natural language

catalogs and is a powerful and simple method for internationalizing

programs.

Usage examples:

ionice – renice you IO activity for the process.

2015-04-13 1 min read Learning

ionice is utility provided by the package util-linux. Description of util-linux:

Description : The util-linux package contains a large variety of low-level system

utilities that are necessary for a Linux system to function. Among

others, Util-linux contains the fdisk configuration tool and the login

program.

With the help of this utility, you can set the scheduler priority for your IO scheduling upto RealTime, but be careful that can make other process sluggish. Example use:

ssh authorized keys – limit ssh session to custom command

2015-03-04 1 min read Learning Linux

If you want a ssh key to be able to run a custom command only and nothing beyond that, then you can use the “command” option in the authorized_keys file of ssh.

For example, to limit user to run only top command with a key, you can add the key like this:

echo 'command="/usr/bin/top" ssh-rsa ' >>~/.ssh/authorized_keys

nice little bash function to search for running processes

2014-10-13 1 min read Bash

Here is a nice little handy function that I use very regurlarly.

You can use this function with parameter to just grep for that or just type psa to see all the running processes.

Just put this in your .bashrc file.

You might find it useful:

psa () 
{ 
    if [[ $1 == "" ]]; then
        ps -eaf;
    else
        ps -eaf | grep --color=auto -i $1;
    fi
}

bash – refer the first parameter from last command quickly

2014-09-22 1 min read Bash

To refer to first parameter from the last command quickly, you can use

Note: This can also be referred as “!!:1“

bash refer parameters from the current command

2014-09-15 1 min read Bash

In bash you can use

to refer to any parameter from the current command, example:

mv ak amit.!#:1.txt
ls amit.ak.txt

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