chmod: implement it

README.md

@@ -63,7 +63,7 @@ compare against the true GNU coreutils version on the Linux-based tests first.
 | ✓ | cat       | Concatenate and write files                      | ✓ |
 |         | chcon     | Change SELinux context of file                   | ✓ |
 |         | chgrp     | Change group ownership                           |         |
-|         | chmod     | Change access permissions                        |         |
+| ✓ | chmod     | Change access permissions                        |         |
 |         | chown     | Change file owner and group                      |         |
 |         | chroot    | Run a command with a different root directory    |         |
 | ✓ | cksum     | Print CRC checksum and byte counts               | ✓ |

common/chmod/args.v

@@ -0,0 +1,127 @@
+module chmod
+
+import common
+
+pub fn parse_args(args []string) Settings {
+	mut s := Settings{}
+	mut operands := []string{}
+	mut mode_set := false
+
+	for i := 0; i < args.len; i++ {
+		a := args[i]
+		if a == '--' {
+			operands << args[i + 1..]
+			break
+		}
+		if a == '--help' {
+			print_help()
+			exit(0)
+		}
+		if a == '--version' {
+			println('chmod (V coreutils) ${common.version}')
+			exit(0)
+		}
+		if a == '-' {
+			operands << a
+			continue
+		}
+		if !a.starts_with('-') {
+			// The mode is the first non-option operand.
+			if !mode_set {
+				s.mode = a
+				mode_set = true
+			} else {
+				operands << a
+			}
+			continue
+		}
+		if a.starts_with('--') {
+			name := a.all_before('=')
+			val := a.all_after('=')
+			has_val := a.contains('=')
+			match name {
+				'--recursive' {
+					s.recursive = true
+				}
+				'--verbose' {
+					s.verbose = true
+				}
+				'--changes' {
+					s.changes = true
+				}
+				'--reference' {
+					v, next := take_value(args, i, val, has_val, name)
+					i = next
+					s.reference = v
+				}
+				'--silent', '--quiet' {}
+				else {
+					common.exit_with_error_message('chmod', "unrecognized option '${a}'")
+				}
+			}
+			continue
+		}
+
+		mut j := 1
+		for j < a.len {
+			c := a[j]
+			match c {
+				`R` {
+					s.recursive = true
+				}
+				`v` {
+					s.verbose = true
+				}
+				`c` {
+					s.changes = true
+				}
+				`f` {}
+				`-` {
+					j++
+					continue
+				}
+				else {
+					common.exit_with_error_message('chmod', "invalid option -- '${c.ascii_str()}'")
+				}
+			}
+			j++
+		}
+	}
+
+	if !mode_set && s.reference == '' {
+		common.exit_with_error_message('chmod', 'missing operand')
+	}
+	if operands.len == 0 {
+		if mode_set {
+			common.exit_with_error_message('chmod', 'missing operand after ‘${s.mode}’')
+		} else {
+			common.exit_with_error_message('chmod', 'missing operand')
+		}
+	}
+	s.operands = operands
+	return s
+}
+
+fn take_value(args []string, i int, inline_val string, has_val bool, name string) (string, int) {
+	if has_val {
+		return inline_val, i
+	}
+	if i + 1 >= args.len {
+		common.exit_with_error_message('chmod', "option '${name}' requires an argument")
+	}
+	return args[i + 1], i + 1
+}
+
+fn print_help() {
+	println('Usage: chmod [OPTION]... MODE[,MODE]... FILE...')
+	println('  or:  chmod [OPTION]... OCTAL-MODE FILE...')
+	println('Change the mode of each FILE to MODE.')
+	println('')
+	println('  -c, --changes   like verbose but report only when a change is made')
+	println('  -f, --silent, --quiet   suppress most error messages')
+	println('  -v, --verbose     output a diagnostic for every file processed')
+	println('      --reference=FILE  use the mode of FILE instead of MODE values')
+	println('  -R, --recursive   change files and directories recursively')
+	println('      --help        display this help and exit')
+	println('      --version     output version information and exit')
+}