Syntax error on bash shell trying to perform a simple calculation

Question

I'm having a syntax error ((standard_in): syntax error)on 3rd and 5th line.

#!/bin/bash
i=`echo "8.8007751822"|bc`
rws = `echo "0.49237251092*$i" |bc`
rmt = `echo "0.85 * $rws"| bc`
dx  = `echo "log ($rws / 0.000001) / 720.0" | bc`;

Can anyone help me?

[ShellCheck](https://www.shellcheck.net/) helpfully points out mistakes like this. — Benjamin W., May 04 '20 at 14:30
The error you describe comes from `bc`, though; if the code you're running is really what you're showing, the error would be `-bash: rws: command not found`. — Benjamin W., May 04 '20 at 14:32
@BenjaminW. I removed the spaces as mentioned on another answer you cited and I have no longer a syntax error but the error command not found. — Miguel Cardoso, May 04 '20 at 14:34
I already used ShellCheck but some suggestions it makes does not work for me for example replacing i=`echo "8.8007751822"` for i=$("8.8007751822") — Miguel Cardoso, May 04 '20 at 14:39
I have reopened the question as it's a mix of things going wrong here; I'll add a community wiki answer. — Benjamin W., May 04 '20 at 14:44

score 1 · Accepted Answer · answered May 04 '20 at 14:46

A few things:

Assignments must not have blanks around the =
i=`echo "8.8007751822"|bc` is a really complicated way to write i=8.8007751822
bc has no function log, there's only l for the natural logarithm (and l requires the -l option to be enabled)

I would move everything into bc instead of calling it multiple times:

bc -l <<'EOF'
i = 8.8007751822
rws = i * 0.49237251092
rmt = 0.85 * rws
dx = (l(rws / 0.000001) / l(10)) / 720
dx
EOF

This prints the value of dx.

Syntax error on bash shell trying to perform a simple calculation

1 Answers1