[common]linux: add HostEtc to switch '/etc' See #175.

README.rst

@@ -17,10 +17,6 @@ psutil functions on some architectures...
 
    Package (a.k.a. directory) structure has been changed!! see `issue 24 <https://github.com/shirou/gopsutil/issues/24>`_
 
-.. highlights:: golang 1.4 will become REQUIRED!
-
-   Since syscall package becomes frozen, we should use golang/x/sys of golang 1.4 as soon as possible.
-
 
 Available Architectures
 ------------------------------------
@@ -63,6 +59,7 @@ The output is below.
 
 You can set an alternative location to /proc by setting the HOST_PROC environment variable.
 You can set an alternative location to /sys by setting the HOST_SYS environment variable.
+You can set an alternative location to /etc by setting the HOST_ETC environment variable.
 
 Documentation
 ------------------------

disk/disk_linux.go

@@ -214,8 +214,7 @@ var fsTypeMap = map[int64]string{
 // Get disk partitions.
 // should use setmntent(3) but this implement use /etc/mtab file
 func DiskPartitions(all bool) ([]DiskPartitionStat, error) {
-
-	filename := "/etc/mtab"
+	filename := common.HostEtc("mtab")
 	lines, err := common.ReadLines(filename)
 	if err != nil {
 		return nil, err

host/host_linux.go

@@ -141,8 +141,8 @@ func Users() ([]UserStat, error) {
 
 func getLSB() (*LSB, error) {
 	ret := &LSB{}
-	if common.PathExists("/etc/lsb-release") {
-		contents, err := common.ReadLines("/etc/lsb-release")
+	if common.PathExists(common.HostEtc("lsb-release")) {
+		contents, err := common.ReadLines(common.HostEtc("lsb-release"))
 		if err != nil {
 			return ret, err // return empty
 		}
@@ -196,19 +196,20 @@ func GetPlatformInformation() (platform string, family string, version string, e
 		lsb = &LSB{}
 	}
 
-	if common.PathExists("/etc/oracle-release") {
+	if common.PathExists(common.HostEtc("oracle-release")) {
 		platform = "oracle"
-		contents, err := common.ReadLines("/etc/oracle-release")
+		contents, err := common.ReadLines(common.HostEtc("oracle-release"))
 		if err == nil {
 			version = getRedhatishVersion(contents)
 		}
-	} else if common.PathExists("/etc/enterprise-release") {
+
+	} else if common.PathExists(common.HostEtc("enterprise-release")) {
 		platform = "oracle"
-		contents, err := common.ReadLines("/etc/enterprise-release")
+		contents, err := common.ReadLines(common.HostEtc("enterprise-release"))
 		if err == nil {
 			version = getRedhatishVersion(contents)
 		}
-	} else if common.PathExists("/etc/debian_version") {
+	} else if common.PathExists(common.HostEtc("debian_version")) {
 		if lsb.ID == "Ubuntu" {
 			platform = "ubuntu"
 			version = lsb.Release
@@ -221,37 +222,37 @@ func GetPlatformInformation() (platform string, family string, version string, e
 			} else {
 				platform = "debian"
 			}
-			contents, err := common.ReadLines("/etc/debian_version")
+			contents, err := common.ReadLines(common.HostEtc("debian_version"))
 			if err == nil {
 				version = contents[0]
 			}
 		}
-	} else if common.PathExists("/etc/redhat-release") {
-		contents, err := common.ReadLines("/etc/redhat-release")
+	} else if common.PathExists(common.HostEtc("redhat-release")) {
+		contents, err := common.ReadLines(common.HostEtc("redhat-release"))
 		if err == nil {
 			version = getRedhatishVersion(contents)
 			platform = getRedhatishPlatform(contents)
 		}
-	} else if common.PathExists("/etc/system-release") {
-		contents, err := common.ReadLines("/etc/system-release")
+	} else if common.PathExists(common.HostEtc("system-release")) {
+		contents, err := common.ReadLines(common.HostEtc("system-release"))
 		if err == nil {
 			version = getRedhatishVersion(contents)
 			platform = getRedhatishPlatform(contents)
 		}
-	} else if common.PathExists("/etc/gentoo-release") {
+	} else if common.PathExists(common.HostEtc("gentoo-release")) {
 		platform = "gentoo"
-		contents, err := common.ReadLines("/etc/gentoo-release")
+		contents, err := common.ReadLines(common.HostEtc("gentoo-release"))
 		if err == nil {
 			version = getRedhatishVersion(contents)
 		}
-	} else if common.PathExists("/etc/SuSE-release") {
-		contents, err := common.ReadLines("/etc/SuSE-release")
+	} else if common.PathExists(common.HostEtc("SuSE-release")) {
+		contents, err := common.ReadLines(common.HostEtc("SuSE-release"))
 		if err == nil {
 			version = getSuseVersion(contents)
 			platform = getSusePlatform(contents)
 		}
 		// TODO: slackware detecion
-	} else if common.PathExists("/etc/arch-release") {
+	} else if common.PathExists(common.HostEtc("arch-release")) {
 		platform = "arch"
 		version = lsb.Release
 	} else if lsb.ID == "RedHat" {

internal/common/common.go

@@ -274,3 +274,7 @@ func HostProc(combineWith ...string) string {
 func HostSys(combineWith ...string) string {
 	return GetEnv("HOST_SYS", "/sys", combineWith...)
 }
+
+func HostEtc(combineWith ...string) string {
+	return GetEnv("HOST_ETC", "/etc", combineWith...)
+}

internal/common/common_test.go

@@ -88,3 +88,10 @@ func TestPathExists(t *testing.T) {
 		t.Error("not exists but return exists")
 	}
 }
+
+func TestHostEtc(t *testing.T) {
+	p := HostEtc("mtab")
+	if p != "/etc/mtab" {
+		t.Errorf("invalid HostEtc, %s", p)
+	}
+}