shell - How to assign an output to a shellscript variable? -

how assign result shell variable?

input:

echo '1+1' | bc -l

output:

2

attempts:

(didn't work)

#!bin/sh a=echo '1+1' | bc -l echo $a 

you're looking shell feature called command-substitution.

there 2 forms of cmd substitution

1. original, stone-age, portable , available in unix-like shells (well all).

   you enclose value generating commands inside of back-ticks characters, i.e.

   $ a=`echo 1+1 | bc -l` $ echo $a 2 $ 

2. modern, less clunky looking, nestable cmd-substitution supplied $( cmd ), i.e.

   $ a=$(echo 1+1 |  bc -l) $ echo $a 2 $ 

your 'she-bang' line says, #!/bin/sh, if you're running on real unix platform, it's /bin/sh original bourne shell, , require use option 1 above.

if try option 2 while still using #!/bin/sh , works, have modern shell. try typing echo ${.sh.version} or /bin/sh -c --version , see if useful information. if version number, you'll want learn features newer shells contain.

speaking of newer features, if using bash, zsh, ksh93+, can rewrite sample code as

a=$(( 1+1 )) 

or if you're doing more math operations, stay inside scope, can use shell feature arithmetic like:

(( b=1+1 )) echo $b 2 

in either case, can avoid process creation, can't floating point arithmetic in shell (whereas can bc).