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Arguments can be passed to the script when it is executed, by writing them as a space-delimited list following the script file name. Inside the script, the $1 variable references the first argument in the command line, $2 the second argument and so forth. The variable $0 references to the current script.
$? is the exit status of the most recently-executed command; by convention, 0 means success and anything else indicates failure. That line is testing whether the grep command succeeded.
$0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1) $9 is the ninth argument.
"$@" Stores all the arguments that were entered on the command line, individually quoted ("$1" "$2" ...). So basically, $# is a number of arguments given when your script was executed. $* is a string containing all arguments. For example, $1 is the first argument and so on.
Traditionally you document your arguments in the usage() function:
#!/bin/bash
programname=$0
function usage {
echo "usage: $programname [-abch] [-f infile] [-o outfile]"
echo " -a turn on feature a"
echo " -b turn on feature b"
echo " -c turn on feature c"
echo " -h display help"
echo " -f infile specify input file infile"
echo " -o outfile specify output file outfile"
exit 1
}
usage
I would recomment using a heredoc:
usage () {
cat <<HELP_USAGE
$0 [-a] -f <file>
-a All the instances.
-f File to write all the log lines
HELP_USAGE
}
instead of:
echo "$0 [-a] -f <file>"
echo
echo "-a All the instances."
echo "-f File to write all the log lines."
I think it is way cleaner than all these echo lines.
I usually wrap my usage in function so I can call it from a -h param etc.
#!/bin/bash
usage() {
cat <<EOM
Usage:
$(basename $0) Explain options here
EOM
exit 0
}
[ -z $1 ] && { usage; }
The Vim bash IDE that does this:
#!/bin/bash
#===============================================================================
#
# FILE: test.sh
#
# USAGE: ./test.sh
#
# DESCRIPTION:
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: ---
# AUTHOR: Joe Brockmeier, [email protected]
# COMPANY: Dissociated Press
# VERSION: 1.0
# CREATED: 05/25/2007 10:31:01 PM MDT
# REVISION: ---
#===============================================================================
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