CODEWITHSUNDEEP
bashshelldoubledivision
user690936
user690936

Reputation: 1035

Dividing double-precision shell variables in a shell script

I am working with shell scripting on Linux.

I have 2 double variables and i want to divide them, and put the results into another variable.

I tried the following (does not work) :

#!/bin/bash
A=333.33
B=111.11
C="$A / $B" | bc -l

although the following does work:

#!/bin/bash
A=333.33
B=111.11
echo "$A / $B" | bc -l

what am i doing wrong?

Thanks Matt

Upvotes: 0

Views: 3094

Answers (4)

Idriss Neumann
Idriss Neumann

Reputation: 3838

When you use a pipe, you must to push an output :

commandA|commandB

The commandA output is pushed in the pipeline and processed by commandB. So commandA must print an output in the stdout stream which is processed by the pipe.

So you could use instead :

C=$(echo "$A / $B"|bc -l)
# or
C=`echo "$A / $B"|bc -l`
# or
C=$(bc -l <<< "$A / $B")
# or 
C=`bc -l <<< "$A / $B"`

If you want to set the result into a variable.

Upvotes: 0

Jacek Sokolowski
Jacek Sokolowski

Reputation: 597

That's the working version:

#!/bin/bash
A=333.33
B=111.11
C=`bc -l <<< "$A/$B"`
echo $C

Upvotes: 0

perreal
perreal

Reputation: 97968

Pipes work on output streams, and:

C="$A / $B" | bc -l

does not send "$A / $B" to the output stream, instead just sends an eof.

You can do this:

C=$(echo "$A / $B" | bc -l)

to get the result into C.

Upvotes: 2

Lennart - Slava Ukraini
Lennart - Slava Ukraini

Reputation: 7171

"$A / $B" is just a string so piping (|) it to "bc -l" doesn't work. A pipe "connects" stdout from one process with stdin on another. echo "$A / $B" on the other hand passes the value of the string to stdout and the pipe passes it to stdin of bc, which works as expected.

Upvotes: 0

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