T3937: rewrite the "show system memory" script in Python

4 files changed, 99 insertions, 34 deletions

diff --git a/op-mode-definitions/show-system.xml.in b/op-mode-definitions/show-system.xml.in
index 18a28868d..b32aee0c2 100644
--- a/op-mode-definitions/show-system.xml.in
+++ b/op-mode-definitions/show-system.xml.in
@@ -104,7 +104,7 @@
             <properties>
               <help>Show system memory usage</help>
             </properties>
-            <command>${vyos_op_scripts_dir}/show_ram.sh</command>
+            <command>${vyos_op_scripts_dir}/show_ram.py</command>
             <children>
               <leafNode name="cache">
                 <properties>
diff --git a/python/vyos/util.py b/python/vyos/util.py
index 849b27d3b..2c4051a7a 100644
--- a/python/vyos/util.py
+++ b/python/vyos/util.py
@@ -489,6 +489,40 @@ def seconds_to_human(s, separator=""):
 
     return result
 
+def bytes_to_human(bytes, initial_exponent=0):
+    """ Converts a value in bytes to a human-readable size string like 640 KB
+
+    The initial_exponent parameter is the exponent of 2,
+    e.g. 10 (1024) for kilobytes, 20 (1024 * 1024) for megabytes.
+    """
+
+    from math import log2
+
+    bytes = bytes * (2**initial_exponent)
+
+    # log2 is a float, while range checking requires an int
+    exponent = int(log2(bytes))
+
+    if exponent < 10:
+        value = bytes
+        suffix = "B"
+    elif exponent in range(10, 20):
+        value = bytes / 1024
+        suffix = "KB"
+    elif exponent in range(20, 30):
+        value = bytes / 1024**2
+        suffix = "MB"
+    elif exponent in range(30, 40):
+        value = bytes / 1024**3
+        suffix = "GB"
+    else:
+        value = bytes / 1024**4
+        suffix = "TB"
+    # Add a new case when the first machine with petabyte RAM
+    # hits the market.
+
+    size_string = "{0:.2f} {1}".format(value, suffix)
+    return size_string
 
 def get_cfg_group_id():
     from grp import getgrnam
diff --git a/src/op_mode/show_ram.py b/src/op_mode/show_ram.py
new file mode 100755
index 000000000..5818ec132
--- /dev/null
+++ b/src/op_mode/show_ram.py
@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2021 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+def get_system_memory():
+    from re import search as re_search
+
+    def find_value(keyword, mem_data):
+        regex = keyword + ':\s+(\d+)'
+        res = re_search(regex, mem_data).group(1)
+        return int(res)
+
+    with open("/proc/meminfo", "r") as f:
+        mem_data = f.read()
+
+    total     = find_value('MemTotal', mem_data)
+    available = find_value('MemAvailable', mem_data)
+    buffers   = find_value('Buffers', mem_data)
+    cached    = find_value('Cached', mem_data)
+
+    used = total - available
+
+    res = {
+      "total":   total,
+      "free":    available,
+      "used":    used,
+      "buffers": buffers,
+      "cached":  cached
+    }
+
+    return res
+
+def get_system_memory_human():
+    from vyos.util import bytes_to_human
+
+    mem = get_system_memory()
+
+    for key in mem:
+        # The Linux kernel exposes memory values in kilobytes,
+        # so we need to normalize them
+        mem[key] = bytes_to_human(mem[key], initial_exponent=10)
+
+    return mem
+
+if __name__ == '__main__':
+    mem = get_system_memory_human()
+
+    print("Total: {}".format(mem["total"]))
+    print("Free:  {}".format(mem["free"]))
+    print("Used:  {}".format(mem["used"]))
+
diff --git a/src/op_mode/show_ram.sh b/src/op_mode/show_ram.sh
deleted file mode 100755
index b013e16f8..000000000
--- a/src/op_mode/show_ram.sh
+++ /dev/null
@@ -1,33 +0,0 @@
-#!/bin/bash
-#
-# Module: vyos-show-ram.sh
-# Displays memory usage information in minimalistic format
-#
-# Copyright (C) 2019 VyOS maintainers and contributors
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 as
-# published by the Free Software Foundation.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-MB_DIVISOR=1024
-
-TOTAL=$(cat /proc/meminfo | grep -E "^MemTotal:" | awk -F ' ' '{print $2}')
-FREE=$(cat /proc/meminfo | grep -E "^MemFree:" | awk -F ' ' '{print $2}')
-BUFFERS=$(cat /proc/meminfo | grep -E "^Buffers:" | awk -F ' ' '{print $2}')
-CACHED=$(cat /proc/meminfo | grep -E "^Cached:" | awk -F ' ' '{print $2}')
-
-DISPLAY_FREE=$(( ($FREE + $BUFFERS + $CACHED) / $MB_DIVISOR ))
-DISPLAY_TOTAL=$(( $TOTAL / $MB_DIVISOR ))
-DISPLAY_USED=$(( $DISPLAY_TOTAL - $DISPLAY_FREE ))
-
-echo "Total: $DISPLAY_TOTAL"
-echo "Free:  $DISPLAY_FREE"
-echo "Used:  $DISPLAY_USED"