cool sed/grep magic to convert output to csv format

I generallly keep doing this a lot, so thought will share with you. Lets assume we are capturing free ouput every min/hour/or whatever. The output looks like this:

Time: Mon Jan 21 23:59:10 AEDT 2019
——————-

total        used        free      shared  buff/cache   available
Mem:          32014        8656        1735        1697       21621       21308
Swap: 51195 75 51120

then we can use some grep and sed to convert this to something like this:

Mon Jan 21 23:59:10 AEDT 2019,32014,8656,1735,1697,21621,21308

This is the code that I used for this:

zgrep -E '^(Time|Mem):' free.20190121.gz |sed -E '/Mem/ s/\s+/,/g'|sed -E 's/^(Time|Mem):\s*//' |sed   ':a;$!N;s/\n//;P'
Explanation:

use zgrep to get the line starting with time or mem
use sed to convert multiple spaces to single space
use sed again to get only the line containing Memory or time
use sed the last time to merge the 2 lines

Get to your ebooks quickly

So this is going to be a little longer post than usual.

To begin with, here is screenshot of how it would look like finally:

We are using “rofi” here to show the menu. So, lets first install that

cat <<EOF >/etc/yum.repos.d/_copr_yaroslav-i3desktop.repo 
[yaroslav-i3desktop]
name=Copr repo for i3desktop owned by yaroslav
baseurl=https://copr-be.cloud.fedoraproject.org/results/yaroslav/i3desktop/fedora-$releasever-$basearch/
type=rpm-md
skip_if_unavailable=True
gpgcheck=1
gpgkey=https://copr-be.cloud.fedoraproject.org/results/yaroslav/i3desktop/pubkey.gpg
repo_gpgcheck=0
enabled=1
EOF

yum install rofi
Once that is done, we will create a small script to look for all our pdf files and display that in the menu, like above. Save this as ~/bin/books-search.sh :
 
#!/usr/bin/env bash
#
# wget 'https://raw.githubusercontent.com/miroslavvidovic/rofi-scripts/master/books-search/books-search.sh'

# -----------------------------------------------------------------------------
# Info:
#   author:    Miroslav Vidovic
#   file:      books-search.sh
#   created:   13.08.2017.-08:06:54
#   revision:  ---
#   version:   1.0
# -----------------------------------------------------------------------------
# Requirements:
#   rofi
# Description:
#   Use rofi to search my books.
# Usage:
#   books-search.sh
# -----------------------------------------------------------------------------
# Script:
# Modified by Amit Agarwal

# Books directory
BOOKS_DIR=/usr/share/texlive/texmf-dist/doc/

# Save find result to F_ARRAY
readarray -t F_ARRAY <<< "$(find "$BOOKS_DIR" -type f -name '*.pdf')"

# Associative array for storing books
# key => book name
# value => absolute path to the file
# BOOKS['filename']='path'
declare -A BOOKS

# Add elements to BOOKS array
get_books() {
    for i in "${!F_ARRAY[@]}"
    do
        path=${F_ARRAY[$i]}
        file=$(basename "${F_ARRAY[$i]}")
        BOOKS+=(["$file"]="$path")
    done
}

# List for rofi
gen_list(){
    for i in "${!BOOKS[@]}"
    do
      echo "$i"
    done
}

main() {
  get_books
  #
 book=$( (gen_list) | rofi -dmenu -lines 10 -width 100 -i -matching 
fuzzy -only-match -location 0 -fake-transparency -p "Book > " )
  book=$( (gen_list) | rofi -dmenu -i -matching fuzzy -only-match -p "Book > " )
  xdg-open "${BOOKS[$book]}"
}

main
exit 0
In the above script, change the BOOKS_DIR to the one that you would like to see. And finally make some cosmetic changes:
cat <<EOF >~/.Xresources 
rofi.color-enabled: true
rofi.opacity:                        50
rofi.width:                          100
rofi.lines:                          10
rofi.columns:                        4
rofi.font:                           System San Francisco Display 8
rofi.color-normal:                   #fdf6e3,#002b36,#eee8d5,#586e75,#eee8d5
rofi.color-urgent:                   #fdf6e3,#dc322f,#eee8d5,#dc322f,#fdf6e3
rofi.color-active:                   #fdf6e3,#268bd2,#eee8d5,#268bd2,#fdf6e3
rofi.color-window:                   #fdf6e3,#002b36
rofi.yoffset:                        0
rofi.xoffset:                        0
rofi.fixed-num-lines:                false
rofi.terminal:                       rofi-sensible-terminal
rofi.ssh-client:                     ssh
rofi.ssh-command:                    {terminal} -e {ssh-client} {host}
rofi.run-command:                    {cmd}
rofi.run-list-command:               
rofi.run-shell-command:              {terminal} -e {cmd}
rofi.window-command:                 xkill -id {window}
rofi.disable-history:                false
rofi.levenshtein-sort:               false
rofi.case-sensitive:                 false
rofi.cycle:                          true
rofi.sidebar-mode:                   false
rofi.auto-select:                    false
rofi.parse-hosts:                    true
rofi.parse-known-hosts:              true
rofi.combi-modi:                     window,run
rofi.fuzzy:                          true
rofi.glob:                           false
rofi.regex:                          false
rofi.tokenize:                       true
rofi.m:                              -1
rofi.line-margin:                    2
rofi.filter:                         
rofi.separator-style:                dash
rofi.hide-scrollbar:                 false
rofi.fullscreen:                     false
rofi.fake-transparency:              true
rofi.dpi:                            -1
rofi.threads:                        1
rofi.scrollbar-width:                8
rofi.scroll-method:                  0
rofi.fake-background:                screenshot
rofi.display-ssh:                    
rofi.display-run:                    
rofi.display-drun:                   
rofi.display-combi:
EOF


xrdb -merge ~/.Xresources
Finally for easy access, you might want to bind a key to lauch the script that we created and voila.

Generate random string for various use case

Some times I need random string, for example to use as email seperator or to use in some API. One way is to use tools like /dev/[u]random or od and other such. But they seem cubersome after I figured this out.

openssl rand <length>
openssl rand 10

This alone without some parameters is not interesting thoug. You can use ‘-base64’ or ‘-hex’ to select the encoding.

So if you execute the above you will get something like this

$ openssl rand -hex 10
591e96110af8aecb760b

$ openssl rand -base64 10
TnuUXuiZXv2ktw==