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--- doc:appunti:prog:python_program_execution [2009/10/01 15:30] – created niccolo
+++ doc:appunti:prog:python_program_execution [2022/07/01 10:56] (current) – [Get the output of a program] niccolo
@@ Line 8: / Line 8: @@
   * popen2.*
   * commands.*
+===== Run a command =====
 Run command with arguments. Wait for command to complete, then return the returncode attribute.
 <code python>
-retcode = subprocess.call(["ls", "-l"])
+retcode = subprocess.call(["mycmd", "myarg"])
 </code>
+Same as above, but run in a subshell (in this case the command may contain shell redirections):
+<code python>
+retcode = subprocess.call("mycmd myarg", shell=True)
+</code>
+===== Get the output of a program =====
+Assign the output to a variable:
+<code python>
+output = subprocess.Popen(["mycmd", "myarg"], stdout=subprocess.PIPE).communicate()[0].decode('utf-8')
+</code>
+Get also the return code, stderr and iterate on the output:
+<code python>
+subproc = subprocess.Popen(["mycmd", "myarg"], stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+output, stderr = subproc.communicate()
+retcode = subproc.returncode
+for line in output.decode('utf-8').splitlines():
+    print(line)
+</code>
+===== Redirect output to a file =====
+<code python>
+file = open("/tmp/cmd_output", "w")
+subprocess.call(["mycmd", "myarg"], stdout=file)
+file.close()
+</code>
+===== Run two commands in a pipe =====
+<code python>
+cmd1 = ["oggdec", "-Q", "-o", "-", src]
+cmd2 = ["lame", "--preset", "cd", "-", dst]
+p1 = subprocess.Popen(cmd1, stdout=subprocess.PIPE)
+p2 = subprocess.Popen(cmd2, stdin=p1.stdout, stdout=subprocess.PIPE)
+p1.stdout.close()
+output = p2.communicate()[0]
+</code>
+===== Write to command standard input =====
+<code python>
+cmd_input = []
+cmd_input.append('line input one')
+cmd_input.append('line input two')
+p = subprocess.Popen('command', stdin=subprocess.PIPE)
+p.communicate(os.linesep.join(cmd_input))
+</code>