initial commit: implement linux

LICENSE

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+BSD 2-Clause License
+
+Copyright (c) 2024, mykola2312.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.

go.mod

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+module github.com/mykola2312/proc4unix
+
+go 1.23.2

linux_test.go

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+//go:build linux
+
+package proc
+
+import "testing"
+
+func TestQuery(t *testing.T) {
+	if _, err := Query(1); err != nil {
+		t.Failed()
+	}
+}

proc.go

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+package proc
+
+type ProcState int
+
+const (
+	PROCSTATE_IDLE   = 1
+	PROCSTATE_STOP   = 2
+	PROCSTATE_RUN    = 3
+	PROCSTATE_UNDEAD = 4
+	PROCSTATE_DEAD   = 5
+	PROCSTATE_LOST   = 6
+)
+
+func Query(pid int) (ProcState, error) {
+	return queryInternal(pid)
+}

proc_linux.go

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+//go:build linux
+
+package proc
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func queryInternal(pid int) (ProcState, error) {
+	status, err := os.ReadFile(fmt.Sprintf("/proc/%d/status", pid))
+	if err != nil {
+		return 0, err
+	}
+
+	for _, line := range strings.Split((string)(status), "\n") {
+		kv := strings.Fields(line)
+		if len(kv) < 2 {
+			continue
+		}
+
+		if kv[0] == "State:" {
+			switch kv[1] {
+			case "D":
+				return PROCSTATE_IDLE, nil
+			case "I":
+				return PROCSTATE_IDLE, nil
+			case "R":
+				return PROCSTATE_RUN, nil
+			case "S":
+				return PROCSTATE_IDLE, nil
+			case "T":
+				return PROCSTATE_STOP, nil
+			case "t":
+				return PROCSTATE_STOP, nil
+			case "X":
+				return PROCSTATE_DEAD, nil
+			case "Z":
+				return PROCSTATE_LOST, nil
+			default:
+				return 0, errors.New("unknown linux state: " + kv[1])
+			}
+		}
+	}
+
+	return 0, errors.New("no state field in linux proc")
+}