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Use $# inside a Bash function to get the number of arguments passed to that function. For example, a call with three arguments—including one containing a space—has a count of three:
my_function() {
printf 'Argument count: %sn' "$#"
}
my_function alpha "two words" gammaThe function prints Argument count: 3. The function’s arguments become its positional parameters while it runs; the function name and $0 are not included in the count.
How to count arguments in a Bash function
The special parameter $# expands to the number of positional parameters currently set. Inside a function, that means the number of arguments passed to the active function call. The GNU Bash Reference Manual, edition 5.3, updated 18 May 2025, defines $# as the count of positional parameters in decimal: GNU Bash manual: Special Parameters.
show_count() {
printf 'Received %s argumentsn' "$#"
}
show_count
show_count red "two words" blueThe first call reports zero; the second reports three. Quoting "$#" is a clear way to pass the resulting value as one argument to printf.
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Check whether the function received the expected number
Test $# before using positional parameters when the function requires a fixed number of inputs:
require_two() {
if (( $# != 2 )); then
printf 'Usage: require_two FIRST SECONDn' >&2
return 2
fi
printf 'first=%s second=%sn' "$1" "$2"
}The arithmetic condition is Bash syntax. If the function receives anything other than two arguments, it prints a usage message to standard error and returns status 2.
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What changes after shift?
$# reports the current number of positional parameters, not a permanently saved count of the original call. Each successful shift removes the first positional parameter, moves the others left, and decreases the count by one. The Bash manual describes this behavior in its section on functions: GNU Bash manual: Shell Functions.
process_all() {
while (( $# > 0 )); do
printf 'Next argument: %sn' "$1"
shift
done
}If later code needs the initial count, save it before shifting:
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process_all() {
local initial_count=$#
printf 'Starting with %s argumentsn' "$initial_count"
while (( $# > 0 )); do
printf 'Next argument: %sn' "$1"
shift
done
}Count arguments versus passing them on
$# gives the count. Use quoted "$@" when you need to inspect or forward the arguments while preserving their boundaries. Each original argument becomes a separate word, so two words remains one argument rather than splitting into two. With no positional parameters, quoted "$@" expands to nothing. See the Bash manual’s explanation of shell parameter expansion: GNU Bash manual: Shell Expansions.
wrapped() {
some_command "$@"
}Common positional-parameter mistakes
- Counting the function name: The function name is not a positional argument, and the function’s
$0remains unchanged.$#counts only positional parameters. - Confusing
$#with$@:$#is a number;"$@"is the argument list, preserving separate arguments when quoted. - Using
$11for the eleventh argument: Bash parses this as$1followed by the literal digit1. Use${11}, and likewise${10}for the tenth argument. The manual documents the brace form for multi-digit positional parameters: GNU Bash manual: Shell Parameter Expansion.
Function arguments and script arguments
Inside a function, positional parameters temporarily represent that function call’s arguments, so $# gives the function’s current count. Outside the function, it refers to the positional parameters of the surrounding script or shell context. Bash documents the positional-parameter behavior for functions in the Shell Functions section.
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