Clear line implementation (sonic-net#284)

* new consutil package - includes helper functions, and show/clear/connect skeletons

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Added connect command skeleton, added show line and clear line skeletons

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Added connect and consutil packages to setup.py and to bash completion

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Added docstrings and "TODO Stub" comments to clear line, show line, and connect line

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Added clear line implementation and added "consutil clear line <linenum>" to clear/main.py

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Fixed "consutil clear" call in clear/main.py

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Changed "connecting" to "connected" in consutil clear line function

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Changed popenWrapper() name to run_command()

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

* Update main.py

Remove SIGTERM magic number

Signed-off-by: Cayla Wanderman-Milne <t-cawand@microsoft.com>

clear/main.py

@@ -250,8 +250,8 @@ def clear_vlan_fdb(vlanid):
 @click.argument('linenum')
 def line(linenum):
     """Clear preexisting connection to line"""
-    # TODO: Stub
-    return
+    cmd = "consutil clear " + str(linenum)
+    run_command(cmd)
 
 if __name__ == '__main__':
     cli()

consutil/lib.py

@@ -20,7 +20,7 @@
 
 # runs command, exit if stderr is written to, returns stdout otherwise
 # input: cmd (str), output: output of cmd (str)
-def popenWrapper(cmd):
+def run_command(cmd):
     proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
     output = proc.stdout.read()
     error = proc.stderr.read()
@@ -40,7 +40,7 @@ def checkDevice(linenum):
 # returns a sorted list of all devices (whose name matches DEVICE_PREFIX)
 def getAllDevices():
     cmd = "ls " + DEVICE_PREFIX + "*"
-    output = popenWrapper(cmd)
+    output = run_command(cmd)
 
     devices = output.split('\n')
     devices = list(filter(lambda dev: re.match(DEVICE_PREFIX + r"\d+", dev) != None, devices))
@@ -52,7 +52,7 @@ def getAllDevices():
 #     maps line number to (pid, process start time)
 def getBusyDevices():
     cmd = 'ps -eo pid,lstart,cmd | grep -E "(mini|pico)com"'
-    output = popenWrapper(cmd)
+    output = run_command(cmd)
     processes = output.split('\n')
 
     # matches any number of spaces then any number of digits
@@ -80,7 +80,7 @@ def getBusyDevices():
 def getBaud(linenum):
     checkDevice(linenum)
     cmd = "sudo stty -F " + DEVICE_PREFIX + str(linenum)
-    output = popenWrapper(cmd)
+    output = run_command(cmd)
 
     match = re.match(r"^speed (\d+) baud;", output)
     if match != None:

consutil/main.py

@@ -31,7 +31,17 @@ def line():
 @click.argument('linenum')
 def clear(linenum):
     """Clear preexisting connection to line"""
-    click.echo("clear line linenum")
+    checkDevice(linenum)
+    linenum = str(linenum)
+
+    busyDevices = getBusyDevices()
+    if linenum in busyDevices:
+        pid, _ = busyDevices[linenum]
+        cmd = "sudo kill -SIGTERM " + pid
+        click.echo("Sending SIGTERM to process " + pid)
+        run_command(cmd)
+    else:
+        click.echo("No process is connected to line " + linenum)
 
 # 'connect' subcommand
 @consutil.command()