work with dollar & awk

Signed-off-by: Arnob kumar saha <[email protected]>

Author: ArnobKumarSaha

basics/dollar.bash

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+#!/bin/bash
+
+
+https://stackoverflow.com/questions/5163144/what-are-the-special-dollar-sign-shell-variables#5163260
+
+$1, $2, $3, ... are the positional parameters.
+"$@" is an array-like construct of all positional parameters, {$1, $2, $3 ...}.
+"$*" is the IFS expansion of all positional parameters, $1 $2 $3 ....
+$# is the number of positional parameters.
+$- current options set for the shell.
+$$ pid of the current shell (not subshell).
+$_ most recent parameter (or the abs path of the command to start the current shell immediately after startup).
+$IFS is the (input) field separator.
+$? is the most recent foreground pipeline exit status.
+$! is the PID of the most recent background command.
+$0 is the name of the shell or shell script.

common/awk.bash

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+#!/bin/bash
+
+# printing first collumn of ps command. 'print $0' & 'print' means all collumn in this case
+ps | awk '{print $1}'
+
+
+# awk -F ":" quoteAndBracket # : is the column seperator 
+#'{print $1"\t"$4}'
+
+awk 'BEGIN{FS=":"; OFS="-"} {print $1,$4}' /etc/passwd
+
+
+# ^/ means every line that begins with a slash, \ is used for escaping
+awk -F "/" '/^\// {print $NF}' /etc/shells # only last word
+
+
+df | awk '/\/dev\/loop/ {print $1"\t"$2 + $3}'
+
+awk 'length($0) > 7' /etc/shells
+
+ps -ef | awk '{ if($NF == "/bin/fish") print $0}'
+
+awk 'BEGIN { for(i=1; i<=10; i++) print "sq of ", i, "is", i*i;}'
+
+awk '$1 ~ /^[b,c]/ {print $0}' .bashrc
+
+awk '{print substr($0, 4)}' numbered.txt
+
+

tricks.sh

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+#!/bin/bash
+
+# AUTHOR : Arnob kumar saha
+# Date created : 11-06-2022
+# Lase modified : 11-06-2022
+
+# DESCRIPTION : This holds some shortcuts and tricks for terminal usage.
+# USAGE : ./tricks.sh
+
+
+cd - # cd to the prevoius directory
+ctrl + L # clear the terminal, scrolling the mouse to above is possible though
+
+pushd <dir> # cd to <dir> & pushes <dir> on a stack, to later cd into that using popd
+popd # cd to the stack's top directory & pod that from stack
+
+ctrl + z # suppose you are editing on vim & u for some reason want to go back to your current terminal
+# without saving ow quitting the editing file
+fg # (foreground) to again get back to editing
+
+sudo !! # exexute the last command with sudo previledges
+ctrl + r # search some previous running command from terminal history
+
+HISTTIMEFORMAT="%Y-%m-%d %T " # now `hostory` command will also show you the data-time of the command execution
+!<ID from `history` command> # to execute a particular command from history
+
+cmatrix # cool hacker-like background !
+ctrl + shift + plusSign # to increase terminal font size
+ctrl + minusSign # to decrease
+
+ctrl + a # move cursor on the beginning of the current line
+ctrl + e # move cursor on the end of the current line
+ctrl + w # delete the last word
+ctrl + u # delete the whole line
+
+tail -f <file> # to watch last few lines of a continously-changing file
+truncate -s 0 <file> # make this file size 0 (Delete everything from this file)
+mount | column -t # 'column' command shows the output in column to look it better
+
+
+