Command line calculator

The basic idea of the following command line calculator is
to perform simple arithmetic operations like

$> c 4 * 5

In this example there are empty spaces around the asterix "*",
which the bash will usually expand to the files in your current directory and
break the calculation.
In the following a variant is present in order to prevent the expansion of the bash:

1. in ~/.alias write

alias c='set -f; call_clc'

2. in ~/.bashrc write

funciton call_clc { clc "$*"; set +f; }

3. create the file ~/bin/clc and write there

echo "$*" | tr -d [:blank:] | bc -l

If the directory ~/bin does not exist, then create it with mkdir ~/bin.
Finally, add export PATH~/bin:$PATH into your ~/.bashrc and execute chmod u+x ~/bin/clc.
Then just source your .bashrc like ". .bashrc" (mind the first and second dot) and your are ready to go.

Now here are other variants, which you could put into your clc file.

# /dev/tty is the userers current shell<br /> echo "$*" | tr -d [:blank:] &>1 | tee /dev/tty | bc

Or another variant with named pipes.

1 2 3 4 5 6

mkfifo pipe echo "$*" | sed -e 's/ //g' | tee pipe & pid_pipe=$! bc &< pipe wait $pid_pipe rm pipe

Simple loops

Here is a small collection of loops you can perform in the bash shell.
Use CompileOnline (ideone works as well)to run the code.
Paste the following sample data into the input.txt file on CompileOnline and run the loops.

Used resources:
SyntaxHighlighter
CompileOnline ABSG


Aang
Korra
Wang
Eska
Tonraq
Kya
Desna
Senna
Bumi
Raava
Unalaq
Varrik
Vaatu

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83

Filename=input.txt echo "# for loop redirection with \"<\"" count=0 name= for k in $(wc -l $Filename | cut -d' ' -f1 | xargs seq) do read name echo "=> $name" let "count += 1" if [ "${name//$'\r'/$''}" == "Bumi" ]; then break fi done < "$Filename" echo "Lines: $count" echo "# while loop redirection with pipe" count=0 name= cat "$Filename" | while read name do echo "=> $name" ((i++)) if [ "${name//$'\r'/$''}" == "Bumi" ]; then break fi done echo "Lines: $count" echo "# while loop redirection with subshell" count=0 name= while read name do echo "=> $name" let "count += 1" if [ "${name//$'\r'/$''}" == "Bumi" ]; then break fi done < <(cat "$Filename") echo "Lines: $count" echo "# while loop redirection with \"<\"" count=0 name= while [ "${name//$'\r'/$''}" != "Bumi" ] do read name echo "=> $name" let "count += 1" done < "$Filename" echo "Lines: $count" echo "# until loop redirection with \"<\"" count=0 name= until [ "${name//$'\r'/$''}" == "Bumi" ] do read name echo "=> $name" let "count += 1" done < "$Filename" echo "Lines: $count" echo "# while loop redirection with exec" count=0 name= exec 3<&0 exec 0<"$Filename" while [ "${name//$'\r'/$''}" != "Bumi" ] do read name echo "=> $name" let "count += 1" done exec 0<&3 exec 3<&- echo "Lines: $count"