$1
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$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. For example, $0, $1, $3, $4 and so on. If you run ./script.sh filename1 dir1, then:
- $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
- ${10} is the tenth argument and must be enclosed in brackets after $9.
- ${11} is the eleventh argument.
$1 and positional parameters example
Create a shell script named demo-args.sh as follows:
#!/bin/bash
script="$0"
first="$1"
second="$2"
tenth="${10}"
echo "The script name : $script"
echo "The first argument : $first"
echo "The second argument : $second"
echo "The tenth and eleventh argument : $tenth and ${11}"
Run it:
chmod +x demo-args.sh ./demo-args.sh foo bar one two a b c d e f z f z h
$1 in bash functions
In bash functions, $1 server as the first bash function parameter and so on.
Examples
Create a new script called func-args.sh:
#!/bin/bash
die(){
local m="$1" # the first arg
local e=$2 # the second arg
echo "$m"
exit $e
}
# if not enough args displayed, display an error and die
[ $# -eq 0 ] && die "Usage: $0 filename" 1
# Rest of script goes here
echo "We can start working the script..."
Run it as follows:
chmod func-args.sh ./func-args.sh
Now try again:
./func-args.sh /etc/hosts
Another example:
fingerprints() {
local file="$1"
while read l; do
[[ -n $l && ${l###} = $l ]] && ssh-keygen -l -f /dev/stdin <<<$l
done < $file
}
See Pass arguments into a function for more information.