Sah::Schema::unix::username - Unix account name


This document describes version 0.021 of Sah::Schema::unix::username (from Perl distribution Sah-Schemas-Unix), released on 2022-09-08.


Sample data and validation results against this schema

 ""  # INVALID

 "foo"  # valid

 "-andy"  # INVALID

 1234  # INVALID

 "andy2"  # valid

 "an dy"  # INVALID

 "an.dy"  # valid

 "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"  # INVALID (Too long)

Using with Data::Sah

To check data against this schema (requires Data::Sah):

 use Data::Sah qw(gen_validator);
 my $validator = gen_validator("unix::username*");
 say $validator->($data) ? "valid" : "INVALID!";

The above schema returns a boolean result (true if data is valid, false if otherwise). To return an error message string instead (empty string if data is valid, a non-empty error message otherwise):

 my $validator = gen_validator("unix::username", {return_type=>'str_errmsg'});
 my $errmsg = $validator->($data);
 # a sample valid data
 $data = "foo";
 my $errmsg = $validator->($data); # => ""
 # a sample invalid data
 $data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
 my $errmsg = $validator->($data); # => "Must match regex pattern qr((?=\\A[A-Za-z0-9._][A-Za-z0-9._-]{0,31}\\z)(?=.*[A-Za-z._-]))"

Often a schema has coercion rule or default value, so after validation the validated value is different. To return the validated (set-as-default, coerced, prefiltered) value:

 my $validator = gen_validator("unix::username", {return_type=>'str_errmsg+val'});
 my $res = $validator->($data); # [$errmsg, $validated_val]
 # a sample valid data
 $data = "foo";
 my $res = $validator->($data); # => ["","foo"]
 # a sample invalid data
 $data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
 my $res = $validator->($data); # => ["Must match regex pattern qr((?=\\A[A-Za-z0-9._][A-Za-z0-9._-]{0,31}\\z)(?=.*[A-Za-z._-]))","aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"]

Data::Sah can also create validator that returns a hash of detailed error message. Data::Sah can even create validator that targets other language, like JavaScript, from the same schema. Other things Data::Sah can do: show source code for validator, generate a validator code with debug comments and/or log statements, generate human text from schema. See its documentation for more details.

Using with Params::Sah

To validate function parameters against this schema (requires Params::Sah):

 use Params::Sah qw(gen_validator);

 sub myfunc {
     my @args = @_;
     state $validator = gen_validator("unix::username*");

Using with Perinci::CmdLine::Lite

To specify schema in Rinci function metadata and use the metadata with Perinci::CmdLine (Perinci::CmdLine::Lite) to create a CLI:

 # in lib/
 our %SPEC;
 $SPEC{myfunc} = {
     v => 1.1,
     summary => 'Routine to do blah ...',
     args => {
         arg1 => {
             summary => 'The blah blah argument',
             schema => ['unix::username*'],
 sub myfunc {
     my %args = @_;

 # in
 use Perinci::CmdLine::Any;

 # in command-line
 % ./ --help
 myapp - Routine to do blah ...

 % ./ --version

 % ./ --arg1 ...


The checking follows POSIX rules: does not begin with a hyphen and only contains [A-Za-z0-9._-].

The above rule allows integers like 1234, which can be confused with UID, so this schema disallows pure integers.

The maximum length is 32 following libc6's limit.

Note that this schema does not check whether the user name exists (has record in the user database e.g. /etc/group). To do that, use the unix::username::exists schema.


Please visit the project's homepage at


Source repository is at


perlancar <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2022, 2020, 2019 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.