[SOLVED] Not understand command what is doing

priyankabade · 05-10-2012, 02:39 AM

awk -F= '{print $4}'
awk -F\( '{print $1}
what will be the output of this command

actual command is
PI=`grep 'Suspended' $FILE | awk -F= '{print $4}' | awk -F\( '{print $1}'`

for which pattern awk will search

plz reply soon

acid_kewpie · 05-10-2012, 02:41 AM

that prints the 4th field, where fields are delimited with an "=" sign, and then the 1st field of that output, where fields are delimited with an opening bracket.

priyankabade · 05-10-2012, 02:48 AM

thanks chris

David the H. · 05-10-2012, 06:22 PM

grep is superfluous here, by the way. awk can do its own pattern matching.

Also, $(..) is highly recommended over `..`

Code:

PI=$( awk -F= '/Suspended/ {print $4}' "$FILE" | awk -F\( '{print $1}' )

You can also reduce it to a single awk instance by using the split function to divide the desired field into an array instead. Or since we want only the first field, the sub function would also work (to remove everything from the first paren on).

Code:

PI=$( awk -F= '/Suspended/ { split($4,a,"(") ; print a[1] }' "$FILE" )

PI=$( awk -F= '/Suspended/ { sub(/[(].*/,"",$4) ; print $4 }' "$FILE" )

See here for details on awk's string functions:
http://www.gnu.org/software/gawk/man...Functions.html

Be sure to quote all of your variables too, to prevent possible word-splitting.

http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes

As a final bit of advice, since environment variables are generally all upper-case, it's good practice to keep your own user variables in lower-case or mixed-case, to help differentiate them.