Error while executing awk command in shell script

Question

I am trying to print the memory details . Total , Free and used memory using a shell script. This is my code -

printf "\nSystem Details\n"
printf "CPU $(cat /proc/cpuinfo | grep "model name" | head -1)" 

printf "Total Memory:"
printf "$(awk '/^Mem/ {print $3}' <(free -m))"

But terminal doesn't display any memory details. It shows this error.

Memory:info.sh: command substitution: line 23: syntax error near unexpected token `('
info.sh: command substitution: line 23: `awk '/^Mem/ {print $3}' <(free -m))"'

check awk is available by running this in your cli . awk 'BEGIN{ print 1}' — Chet
– Chet, Commented Jun 4, 2016 at 6:42

John1024 · Accepted Answer · 2016-06-04 19:06:26Z

2

Let's run the line in question under bash:

$ printf "$(awk '/^Mem/ {print $3}' <(free -m))"
5603$

It works. Now let's try it under dash:

$ printf "$(awk '/^Mem/ {print $3}' <(free -m))"
dash: 1: Syntax error: "(" unexpected

Now, we see the syntax error about the unexpected (. The error is because dash does not support process substitution.

If you want to run under dash or similar shells, the solution is to use a pipeline instead:

$ printf "$(free -m | awk '/^Mem/{print $3}')"
5623$

Process substitution is supported by bash, zsh, Ksh88, ksh93, but not pdksh, mksh, or dash. The pipeline approach should be supported by all POSIX shells.

Improvement

The above works as long as the output does not contain printf-active characters. It is much better practice to use an explicit format string and thereby avoid unpleasant surprises:

printf "%s" "$(free -m | awk '/^Mem/{print $3}')"

edited Jun 4, 2016 at 19:06

answered Jun 4, 2016 at 6:49

John1024

115k15 gold badges151 silver badges183 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

John1024 Over a year ago

@EdMorton Very true. Added to answer.

Collectives™ on Stack Overflow

Error while executing awk command in shell script

1 Answer 1

Improvement

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Improvement

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related