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@geoom
Created June 7, 2013 13:19
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For those scripts needing a single do-it-all tool, a Swiss army knife, there is Perl. Perl combines the capabilities of sed and awk, and throws in a large subset of C, to boot. It is modular and contains support for everything ranging from object-oriented programming up to and including the kitchen sink. Short Perl scripts lend themselves to emb…
#!/bin/bash
# Adds up a specified column (of numbers) in the target file.
# Floating-point (decimal) numbers okay, because awk can handle them.
ARGS=2
E_WRONGARGS=85
if [ $# -ne "$ARGS" ] # Check for proper number of command-line args.
then
echo "Usage: `basename $0` filename column-number"
exit $E_WRONGARGS
fi
filename=$1
column_number=$2
# Passing shell variables to the awk part of the script is a bit tricky.
# One method is to strong-quote the Bash-script variable
#+ within the awk script.
# $'$BASH_SCRIPT_VAR'
# ^ ^
# This is done in the embedded awk script below.
# See the awk documentation for more details.
# A multi-line awk script is here invoked by
# awk '
# ...
# ...
# ...
# '
# Begin awk script.
# -----------------------------
awk '
{ total += $'"${column_number}"'
}
END {
print total
}
' "$filename"
# -----------------------------
# End awk script.
# It may not be safe to pass shell variables to an embedded awk script,
#+ so Stephane Chazelas proposes the following alternative:
# ---------------------------------------
# awk -v column_number="$column_number" '
# { total += $column_number
# }
# END {
# print total
# }' "$filename"
# ---------------------------------------
exit 0
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