Using && in subprocess.Popen for command chaining?

问题:

I'm using subprocess.Popen with Python, and I haven't come across an elegant solution for joining commands (i.e. foobar&& bizbang) via Popen.

I could do this:

p1 = subprocess.Popen(["mmls", "WinXP.E01"], stdout=subprocess.PIPE) result = p1.communicate()[0].split("\n") for line in result:     script_log.write(line)  script_log.write("\n")  p1 = subprocess.Popen(["stat", "WinXP.E01"], stdout=subprocess.PIPE) result = p1.communicate()[0].split("\n") for line in result:     script_log.write(line) 

---

But that really isn't very aesthetically pleasing (especially if I'm daisy-chaining multiple commands via Popen.

---

I'd like to replicate this output in as few command blocks as possible.

not@work ~/ESI/lab3/images $ mmls WinXP.E01 && echo -e "\n" && stat WinXP.E01 DOS Partition Table Offset Sector: 0 Units are in 512-byte sectors       Slot    Start        End          Length       Description 00:  Meta    0000000000   0000000000   0000000001   Primary Table (#0) 01:  -----   0000000000   0000000062   0000000063   Unallocated 02:  00:00   0000000063   0020948759   0020948697   NTFS (0x07) 03:  -----   0020948760   0020971519   0000022760   Unallocated     File: `WinXP.E01'   Size: 4665518381  Blocks: 9112368    IO Block: 4096   regular file Device: 14h/20d Inode: 4195953     Links: 1 Access: (0644/-rw-r--r--)  Uid: ( 1000/    nott)   Gid: ( 1000/    nott) Access: 2013-03-16 23:20:41.901326579 -0400 Modify: 2013-03-04 10:05:50.000000000 -0500 Change: 2013-03-13 00:25:33.254684050 -0400  Birth: - 

---

Any suggestions?

Note: I'd like to avoid typing this into subprocess.Popen

p1 = subprocess.Popen(["mmls WinXP.E01 && echo -e '\n' && stat WinXP.E01"], stdout=subprocess.PIPE) 

回答1:

&& is a shell operator, POpen does not use a shell by default.

If you want to use shell functionality use shell=True in your POpen call, but be aware that it is slightly slower/more memory intensive.

p1 = subprocess.Popen(["mmls", "WinXP.E01", "&&", "echo", "-e", "\"\n\"", "&&", "stat", "WinXP.E01"],                       stdout=subprocess.PIPE, shell=True) 

回答2:

How about this:

from subprocess import Popen, PIPE  def log_command_outputs(commands):     processes = [Popen(cmd, stdout=PIPE) for cmd in commands]     outputs = [proc.communicate()[0].split() for proc in processes]     for output in outputs:         for line in output:             script_log.write(line)         script_long.write("\n") 

This starts the commands in parallel, which might make it a little faster than doing them one by one (but probably not by a large margin). Since the communicate calls are sequential though, any command that has a large output (more than a pipe's buffer) will block until it's turn comes to be cleaned up.

For your example command chain, you'd call:

log_command_outputs([["mmls", "WinXP.E01"], ["stat", "WinXP.E01"]]) 

文章来源: Using && in subprocess.Popen for command chaining?