Implement link util

README.md

@@ -48,7 +48,7 @@ count below and mark it as done in this README.md. Thanks!
 GNU coreutils. They are not 100% compatiable. If you encounter different behaviors,
 compare against the true GNU coreutils version on the Linux-based tests first.
 
-## Completed (73/109) - 67% done!
+## Completed (74/109) - 68% done!
 
 |  Done   | Cmd       | Descripton                                       | Windows | 
 | :-----: | --------- | ------------------------------------------------ | ------- |
@@ -94,7 +94,7 @@ compare against the true GNU coreutils version on the Linux-based tests first.
 |         | install   | Copy files and set attributes                    |         |
 |         | join      | Join lines on a common field                     | ✓ |
 |         | kill      | Send a signal to processes                       | ✓ |
-|         | link      | Make a hard link via the link syscall            | ✓ |
+| ✓ | link      | Make a hard link via the link syscall            | ✓ |
 | ✓ | ln        | Make links between files                         | ✓ |
 | ✓ | logname   | Print current login name                         | ✓ |
 | ✓ | ls        | List directory contents                          |         |
@@ -129,7 +129,7 @@ compare against the true GNU coreutils version on the Linux-based tests first.
 | ✓ | sha256sum | Print or check SHA-2 256 bit digests             | ✓ |
 | ✓ | sha384sum | Print or check SHA-2 384 bit digests             | ✓ |
 | ✓ | sha512sum | Print or check SHA-2 512 bit digests             | ✓ |
-|         | shred     | Remove files more securely                       | ✓ |
+| ✓ | shred     | Remove files more securely                       | ✓ |
 | ✓ | shuf      | Shuffling text                                   | ✓ |
 | ✓ | sleep     | Delay for a specified time                       | ✓ |
 | ✓ | sort      | Sort text files                                  | ✓ |

common/testing/testing.v

@@ -186,7 +186,7 @@ pub fn same_results(cmd1 string, cmd2 string) bool {
 	return cmd1_res.exit_code == cmd2_res.exit_code && noutput1 == noutput2
 }
 
-fn normalise(s string) string {
+pub fn normalise(s string) string {
 	return s.replace_each(['‘', "'", '’', "'"]).replace('  ', ' ').replace('  ', ' ').replace('  ',
 		' ').replace(', ', ' ').split_into_lines().join('\n').trim_space()
 }

src/link/link.v

@@ -0,0 +1,42 @@
+module main
+
+import common
+import os
+
+const app = common.CoreutilInfo{
+	name:        'link'
+	description: 'Call the link function to create a link named FILE2 to an existing FILE1.'
+}
+
+struct Settings {
+mut:
+	files []string
+}
+
+fn args() Settings {
+	mut fp := app.make_flag_parser(os.args)
+	mut st := Settings{}
+	st.files = fp.remaining_parameters()
+	match st.files.len {
+		0 { app.quit(message: 'missing operand') }
+		1 { app.quit(message: "missing operand after '${st.files[0]}'", show_help_advice: true) }
+		2 {}
+		else { app.quit(message: "extra operand '${st.files[2]}'", show_help_advice: true) }
+	}
+
+	return st
+}
+
+fn link(settings Settings) !int {
+	mut exit_code := 0
+	os.link(settings.files[0], settings.files[1]) or {
+		app.quit(
+			message: "cannot create link '${settings.files[1]}' to '${settings.files[0]}': ${err.msg()}"
+		)
+	}
+	return exit_code
+}
+
+fn main() {
+	exit(link(args()) or { common.err_programming_error })
+}

src/link/link_test.v

@@ -0,0 +1,67 @@
+module main
+
+import common.testing
+import os
+
+const rig = testing.prepare_rig(util: 'link')
+
+fn testsuite_begin() {
+}
+
+fn testsuite_end() {
+}
+
+fn test_help_and_version() {
+	rig.assert_help_and_version_options_work()
+}
+
+fn test_compare() {
+	$if windows {
+		// The coreutils used on Windows does not produce the exact
+		// same error messages
+		rig.assert_same_exit_code('a')
+		rig.assert_same_exit_code('a b')
+		rig.assert_same_exit_code('a b c')
+		rig.assert_same_exit_code('a b c d e f')
+		os.mkdir('d')!
+		rig.assert_same_exit_code('d e')
+		os.rmdir('d')!
+	} $else {
+		rig.assert_same_results('a')
+		rig.assert_same_results('a b')
+		rig.assert_same_results('a b c')
+		rig.assert_same_results('a b c d e f')
+		os.mkdir('d')!
+		rig.assert_same_results('d e')
+		os.rmdir('d')!
+	}
+
+	// We can't use assert_same_results here because the hard link will already
+	// exist when the second util is called
+	os.write_file('a', '12345')!
+	cmd1_res := rig.call_orig('a b')
+	assert os.is_file('a')
+	assert os.is_file('b')
+	assert os.read_file('b') or { '' } == '12345'
+	mut f := os.open_append('b')!
+	f.write_string('67890')!
+	f.close()
+	assert os.read_file('a') or { '' } == '1234567890'
+	os.rm('b')!
+	os.rm('a')!
+
+	os.write_file('a', '12345')!
+	cmd2_res := rig.call_new('a b')
+	assert os.is_file('a')
+	assert os.is_file('b')
+	assert os.read_file('b') or { '' } == '12345'
+	f = os.open_append('b')!
+	f.write_string('67890')!
+	f.close()
+	assert os.read_file('a') or { '' } == '1234567890'
+	os.rm('b')!
+	os.rm('a')!
+
+	assert cmd1_res.exit_code == cmd2_res.exit_code
+	assert testing.normalise(cmd1_res.output) == testing.normalise(cmd2_res.output)
+}