bashnotesforprofessionals.bash

# Note that spaces cannot be used around the `=` assignment operator
whom_variable="World"
# Use printf to safely output the data
printf "Hello, %s\n" "$whom_variable"
> Hello, World


#If you want to bash to expand your argument, you can use Weak Quoting:
#!/usr/bin/env bash
world="World"
echo "Hello $world"
> Hello World
#If you don't want to bash to expand your argument, you can use Strong Quoting:
#!/usr/bin/env bash
world="World"
echo 'Hello $world'
>Hello $world

#DEBUG
bash -x hello.sh
#The -x argument enables you to walk through each line in the script. One good example is here:


#change to the Directory of the Script
cd "$(dirname "$(readlink -f "$0")")"


#list Files Without Using `ls`
printf "%s\n" *

files=( * )
for file in "${files[@]}"; do
 echo "$file"
done


#list files sorted with size
ls -l -S ./Fruits

#cat options
cat -n #show line numbers
#To skip empty lines when counting lines, use the --number-nonblank, or simply -b.
cat -b file
>1 line 1
 2 line 2
 3 line 4
 4 line 5
cat -A #show special characters,tabs,linefeeds

#primary purpose of cat.
cat file1 file2 file3 > file_all
cat file1.gz file2.gz file3.gz > combined.gz

#print file reverse
tac file.txt


#A here document can be used to inline the contents of a file into a command line or a script:
cat <<END >file
Hello, World.
END
#The token after the << redirection symbol is an arbitrary string which needs to occur alone on a line (with no leading
#or trailing whitespace) to indicate the end of the here document. You can add quoting to prevent the shell from
#performing command substitution and variable interpolation:
cat <<'fnord'
Nothing in `here` will be $changed
fnord
#(Without the quotes, here would be executed as a command, and $changed would be substituted with the value of
#the variable changed -- or nothing, if it was undefined.)

#show non printable characters
echo '” `' | cat -A
>M-bM-^@M-^] `$

#alias
alias now='date'
unalias {alias_name}

echo There are ${#BASH_ALIASES[*]} aliases defined.

for ali in "${!BASH_ALIASES[@]}"; do
 printf "alias: %-10s triggers: %s\n" "$ali" "${BASH_ALIASES[$ali]}"
done

alias -p