The Linux Shell provides a useful calculator which is bc. It may be short for ‘bash calculator’. The bc takes the following parameters.
1 2 3 4 5 6 7 8 9 | root@uploadbeta:~# bc --help usage: bc [options] [file ...] -h --help print this usage and exit -i --interactive force interactive mode -l --mathlib use the predefined math routines -q --quiet don't print initial banner -s --standard non-standard bc constructs are errors -w --warn warn about non-standard bc constructs -v --version print version information and exit |
root@uploadbeta:~# bc --help usage: bc [options] [file ...] -h --help print this usage and exit -i --interactive force interactive mode -l --mathlib use the predefined math routines -q --quiet don't print initial banner -s --standard non-standard bc constructs are errors -w --warn warn about non-standard bc constructs -v --version print version information and exit
Some quick examples of using bash are:
1 2 3 4 5 6 | root@uploadbeta:~# echo 'scale=30;sqrt(2)' | bc 1.414213562373095048801688724209 root@uploadbeta:~# echo '355/113.0' | bc 3 root@uploadbeta:~# echo '6^2' | bc 36 |
root@uploadbeta:~# echo 'scale=30;sqrt(2)' | bc 1.414213562373095048801688724209 root@uploadbeta:~# echo '355/113.0' | bc 3 root@uploadbeta:~# echo '6^2' | bc 36
By default, the bc will be in interactive mode if no input string/file is given.
1 2 3 4 5 6 7 8 9 | root@uploadbeta:~# bc bc 1.06.95 Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type `warranty'. 1+2 3 quit root@uploadbeta:~# |
root@uploadbeta:~# bc bc 1.06.95 Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type `warranty'. 1+2 3 quit root@uploadbeta:~#
Under interactive mode, you type in expressions and results are computed and printed out until the ‘quit’ command is given.
As you already see in the above example, the bc uses sqrt() function to compute the square root, we might wrap this up a little bit in a bash shell.
1 2 3 4 5 6 7 8 | #!/bin/bash [ $# -ne 1 ] && { echo 'Usage: sqrt number' exit 1 } || { echo -e "sqrt($1)\nquit\n" | bc -q -i | head -2 | tail -1 } |
#!/bin/bash
[ $# -ne 1 ] && {
echo 'Usage: sqrt number'
exit 1
} || {
echo -e "sqrt($1)\nquit\n" | bc -q -i | head -2 | tail -1
}1 2 3 4 5 6 | root@uploadbeta:~# chmod +x ./sqrt root@uploadbeta:~# ./sqrt 3 1 root@uploadbeta:~# ./sqrt 3.0 1.7 root@uploadbeta:~# |
root@uploadbeta:~# chmod +x ./sqrt root@uploadbeta:~# ./sqrt 3 1 root@uploadbeta:~# ./sqrt 3.0 1.7 root@uploadbeta:~#
We check the number of parameters (shell variable $#), if it is not one, then print the usage (compound command &&) otherwise (compound command ||) prints the sqrt using bc
The echo -e will treat the escape characters and head -2 | tail -1 will disregard the first line (sqrt($1)) and last line (quit) in the printout.
You can also write it this way:
1 2 3 4 5 6 7 8 | #!/bin/bash if [ $# -ne 1 ]; then echo 'Usage: sqrt number' exit 1 else echo -e "sqrt($1)\nquit\n" | bc -q -i | head -2 | tail -1 fi |
#!/bin/bash if [ $# -ne 1 ]; then echo 'Usage: sqrt number' exit 1 else echo -e "sqrt($1)\nquit\n" | bc -q -i | head -2 | tail -1 fi
–EOF (The Ultimate Computing & Technology Blog) —
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