os: basic proof of concept stdout capture; autofree: small fixes

vlib/os/os_nix.c.v

@@ -159,6 +159,54 @@ pub fn exec(cmd string) ?Result {
 	}
 }
 
+pub struct  Command {
+mut:
+	f voidptr
+pub mut:
+	eof bool
+pub:
+	path string
+	redirect_stdout bool
+}
+
+//pub fn command(cmd Command) Command {
+//}
+
+pub fn (mut c Command) start()? {
+	pcmd := '$c.path 2>&1'
+	c.f = vpopen(pcmd)
+	if isnil(c.f) {
+		return error('exec("$c.path") failed')
+	}
+}
+
+pub fn (mut c Command) read_line() string {
+	buf := [4096]byte{}
+	mut res := strings.new_builder(1024)
+	unsafe {
+		for C.fgets(charptr(buf), 4096, c.f) != 0 {
+			bufbp := byteptr(buf)
+			len := vstrlen(bufbp)
+			for i in 0..len {
+				if int(bufbp[i]) == `\n` {
+					res.write_bytes(bufbp, i)
+					return res.str()
+				}
+			}
+			res.write_bytes(bufbp, len)
+		}
+	}
+	c.eof = true
+	return res.str()
+}
+
+pub fn (c &Command) close()? {
+	exit_code := vpclose(c.f)
+	if exit_code == 127 {
+		return error_with_code('error', 127)
+	}
+}
+
 pub fn symlink(origin string, target string) ?bool {
 	res := C.symlink(charptr(origin.str), charptr(target.str))
 	if res == 0 {

vlib/os/os_test.v

@@ -503,3 +503,18 @@ fn test_write_file_array_structs() {
 	assert rarr.len == maxn
 	// eprintln( rarr.str().replace('\n', ' ').replace('},', '},\n'))
 }
+
+fn test_stdout_capture() {
+	/*
+mut cmd := os.Command{
+	path:'cat'
+	redirect_stdout: true
+}
+cmd.start()
+for !cmd.eof {
+	line := cmd.read_line()
+	println('line="$line"')
+}
+cmd.close()
+*/
+}