How do wildcards match several filenames in a command-line argument?

A wildcard is a pattern that can stand for part of a filename. Common patterns include *, for zero or more characters, and ?, for a character position. For example, report-*.txt describes names beginning with report- and ending with .txt. The exact matching behavior depends on the shell or command, so check it where you plan to use it.

In Bash, an unquoted *, ?, or [ can trigger filename expansion: Bash replaces the pattern with a sorted list of matching names before starting the command. By default, a pattern with no matches remains unchanged, though shell options can change that. Names beginning with . generally need a pattern that explicitly starts with a dot, unless a setting changes the behavior. [S1]

To inspect matches in Bash without opening or changing files, try:

printf '%s\n' report-*.txt

Read the output and confirm it shows the intended filenames. If there are no matches under Bash’s default behavior, the pattern itself may be printed.

In the Bash example, the shell expands the pattern first, so the program receives the matching filenames rather than the original wildcard. Quoting it, as in printf '%s\n' 'report-*.txt', prevents Bash from expanding it; printf then prints the literal pattern.

PowerShell has its own wildcard behavior. Its patterns include *, ?, and bracket expressions, but support depends on the operator or command parameter. The documentation gives Get-ChildItem as an example of a command that accepts filename patterns; not every parameter accepts them. [S2] You can inspect a matching list with:

Get-ChildItem -Path 'report-*.txt'

Bash and PowerShell patterns should not be assumed interchangeable. A program may also define its own pattern rules, so check the relevant command’s documentation or help.

In Bash, report-??.txt describes names with two character positions between report- and .txt. report-[ab].txt uses a bracket expression. These are useful patterns to inspect, but verify their behavior in the shell you are using. [S1]

For dot-prefixed names in Bash, try an explicit pattern such as .*.txt if that is what you intend to check. By default, a pattern generally needs an explicit leading dot to match names beginning with one. [S1]

Run the listing check and compare each printed name with your intended rule. If the output is surprising, stop and investigate rather than using the pattern in another command. The listing shows matches for that shell or command in that location at that time; it does not establish what another tool or a later run will match.

Check whether the specific command argument accepts wildcards and whether the shell or the command will interpret the pattern. In PowerShell, wildcard support is parameter-specific. For a filename containing literal wildcard characters, the documentation describes escaping them or using -LiteralPath to avoid treating them as a pattern. [S2] In Bash, quoting prevents shell expansion, but the receiving program may still interpret the quoted pattern itself.

Before using an action command, confirm the intended location and inspect the listing there. Make sure every listed name is intended; if the output is empty, unexpectedly broad, or includes an unwanted name, do not proceed until you understand why. A preview checks the matches, not what a later command will do with them.