awk: syntax error near unexpected token `('

Question

I tried to assign the output of an awk command to a variable:

USERS=$(awk '/\/X/ {print $1}' <(w))

This line is part of the following script:

#!/bin/sh

INTERFACE=$1 # The interface which is brought up or down
STATUS=$2 # The new state of the interface

case "$STATUS" in
    up) # $INTERFACE is up

        if pidof dropbox; then
          killall dropbox
        fi

        USERS=$(awk '/\/X/ {print $1}' <(w))

        for user in $USERS; do
            su -c "DISPLAY=$(awk '/\/X/ {print $11}' <(w)) dropboxd &" $user
        done
        ;;
    down) # $INTERFACE is down
        ;;
esac

However, I get the following error:

script: command substitution: line 14: syntax error near unexpected token `('
script: command substitution: line 14: `awk '/\/X/ {print $1}' <(w))'

All brackets are closed. Where is the syntax error?

"line 14"? It looks like the syntax error may be introduced earlier in your script. — johnsyweb, Oct 27 '13 at 11:31
@piokuc: Try `cat <(w)` to see how [`<()` process substitution](http://tldp.org/LDP/abs/html/process-sub.html) works. — johnsyweb, Oct 27 '13 at 11:32
@piokuc When executed in a shell, it shows me the username of the currently logged in user of the running X session: `~ $ awk '/\/X/ {print $1}' <(w) orschiro` — orschiro, Oct 27 '13 at 11:35

score 7 · Accepted Answer · answered Oct 27 '13 at 11:52

7

I'm assuming because you are using #!/bin/sh and not #!/bin/bash that process substitution is not available (or you have a version of bash that doesn't support process subsitiution, pre 4.X.X). Switch to bash or just pipe w to your awk command:

USERS=$(w | awk '/\/X/ {print $1}')

answered Oct 27 '13 at 11:52

Chris Seymour

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Thanks for the essential hint! I did not know that sh does not support process substitution. – orschiro Oct 27 '13 at 11:54
The piping of `w` to `awk` isn't working for me. I use GNU Bash-4.2 – EverythingRightPlace Oct 27 '13 at 11:58
@bashophil does you system have the `w` command? What error message do you see? – Chris Seymour Oct 27 '13 at 12:08
@orschiro yes `sh` is a *(old)* lightweight shell, if you are using anything fancy you almost certainly want `bash`. – Chris Seymour Oct 27 '13 at 12:08
@sudo_O `w` is working in the terminal and in a Bash-script. But the grepping with `awk` seems not to work, there is just no output (no error). – EverythingRightPlace Oct 27 '13 at 12:17
I recommend changing your command to be `USERS=$(ps ux | awk '/\/[X]/ { print $1 }' | sort -u)`. – johnsyweb Oct 27 '13 at 12:18
@bashophil that means the command is working fine but the output of `w` doesn't contain the pattern `/\/X/` which is literally `/X`. – Chris Seymour Oct 27 '13 at 12:25
@sudo_O Yup, lol I misread that part with the X-session. Makes sense now. Ty – EverythingRightPlace Oct 27 '13 at 12:27

awk: syntax error near unexpected token `('

1 Answers1