python调用Linux脚本或者shell指令的几种方法
python如何调用脚本或者shell指令?
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方法1:
os.system()
只得到命令成功与否的执行状态
>>> import os >>> os.system('free -m') total used free shared buffers cached Mem: 474 463 11 0 13 29 -/+ buffers/cache: 420 54 Swap: 1023 415 608 >>> ret=os.system('free -m') total used free shared buffers cached Mem: 474 464 10 0 12 30 -/+ buffers/cache: 420 53 Swap: 1023 415 608 >>> print ret #返回状态码是0,表示shell执行成功 0
方法2:
os.popen
通过 os.popen() 返回的是 file read 的对象,对其进行读取 read() 的操作可以看到执行的输出。但是无法读取程序执行的返回值)
>>> import os >>> output = os.popen('free -mt') >>> print output.read() total used free shared buff/cache available Mem: 7823 3445 215 64 4162 3864 Swap: 3071 270 2801 Total: 10895 3716 3016
方法3:
commands.getstatusoutput() && commands.getoutput()
commands.getstatusoutput() 既可以输出执行成功与否的状态,也会输出执行结果
commands.getoutput() 只输出执行结果
>>> import commands >>> (status, output) = commands.getstatusoutput('free -mt') >>> print status 0 >>> print output total used free shared buff/cache available Mem: 7823 3475 188 64 4159 3834 Swap: 3071 270 2801 Total: 10895 3746 2989 >>> output = commands.getoutput('free -mt') >>> print output total used free shared buff/cache available Mem: 7823 3475 188 64 4159 3834 Swap: 3071 270 2801 Total: 10895 3746 2989
当命令调用错误时:
>>> (status, output) = commands.getstatusoutput('free -aaa') >>> print status 256 >>> print output free: invalid option -- 'a' Usage: free [options] Options: -b, --bytes show output in bytes -k, --kilo show output in kilobytes -m, --mega show output in megabytes -g, --giga show output in gigabytes --tera show output in terabytes -h, --human show human-readable output --si use powers of 1000 not 1024 -l, --lohi show detailed low and high memory statistics -t, --total show total for RAM + swap -s N, --seconds N repeat printing every N seconds -c N, --count N repeat printing N times, then exit -w, --wide wide output --help display this help and exit -V, --version output version information and exit For more details see free(1).
方法4:
subprocess子进程(功能强大,最常使用的方式)
subprocess模块是python从2.4版本开始引入的模块。主要用来取代 一些旧的模块方法,如os.system、os.spawn*、os.popen*、commands.*等。subprocess通过子进程来执行外部指令,并通过input/output/error管道,获取子进程的执行的返回信息。
(1)subprocess.call执行命令,并返回状态,类似os.system(),shell=True可以直接调用命令,而shell=False命令和参数需要分开
>>> output = subprocess.call(['free','-mt'],shell=False) total used free shared buff/cache available Mem: 7823 3446 209 64 4167 3863 Swap: 3071 270 2801 Total: 10895 3716 3011 >>> print output 0 >>> output = subprocess.call('free -mt',shell=True) total used free shared buff/cache available Mem: 7823 3445 209 64 4167 3863 Swap: 3071 270 2801 Total: 10895 3716 3010 >>> print output 0
(2)subprocess.check_call 用法与subprocess.call()类似,区别是,当返回值不为0时,还会抛出python层面的异常
>>> output = subprocess.call('la -ltrh',shell=True) /bin/sh: la: command not found >>> output = subprocess.check_call('la -ltrh',shell=True) /bin/sh: la: command not found Traceback (most recent call last): File "", line 1, in File "/usr/lib64/python2.7/subprocess.py", line 542, in check_call raise CalledProcessError(retcode, cmd) subprocess.CalledProcessError: Command 'la -ltrh' returned non-zero exit status 127
(3)suprocess.Popen()
在一些复杂场景中,我们需要将一个进程的执行输出作为另一个进程的输入。在另一些场景中,我们需要先进入到某个输入环境,然后再执行一系列的指令等。这个时候我们就需要使用到suprocess.Popen()方法。该方法有以下参数:
args:shell命令,可以是字符串,或者序列类型,如list,tuple。
stdin,stdout,stderr:分别表示程序的标准输入,标准输出及标准错误
shell:True或False
cwd:用于设置子进程的当前目录
env:用于指定子进程的环境变量。如果env=None,则默认从父进程继承环境变量
universal_newlines:不同系统的的换行符不同,当该参数设定为true时,则表示使用\n作为换行符
如:在/usr/local/MySQL下创建一个suprocesstest的目录:
>>> output = subprocess.Popen('mkdir subprocesstest',shell=True,cwd='/usr/local/mysql') >>> output = subprocess.Popen('ls -ld sub*',shell=True,cwd='/usr/local/mysql') drwxr-xr-x 2 mysqladmin dba 6 Mar 5 16:12 subprocesstest
使用标准输出stdout和标准错误stderr,不会把输出结果返回到显示屏上
>>> child1 = subprocess.Popen('free -mt',shell=True) >>> total used free shared buff/cache available Mem: 7823 3446 204 64 4172 3863 Swap: 3071 270 2801 Total: 10895 3716 3006 >>> child1 = subprocess.Popen('free -mt',shell=True,stdout=subprocess.PIPE) >>> output = child1.communicate() >>> print output (' total used free shared buff/cache available\nMem: 7823 3446 201 64 4175 3862\nSwap: 3071 270 2801\nTotal: 10895 3717 3002\n', None) >>> child1 = subprocess.Popen('lss',shell=True,stdout=subprocess.PIPE) /bin/sh: lss: command not found >>> child1 = subprocess.Popen('lss',shell=True,stdout=subprocess.PIPE,stderr=subprocess.PIPE) >>> output = child1.communicate() >>> print output ('', '/bin/sh: lss: command not found\n')
将一个子进程的输出,作为另一个子进程的输入,相当于管道,如:cat /etc/passwd|grep 'root'
>>> import subprocess >>> child1 = subprocess.Popen(["cat","/etc/passwd"], stdout=subprocess.PIPE) >>> child2 = subprocess.Popen(["grep","root"],stdin=child1.stdout, stdout=subprocess.PIPE) >>> output = child2.communicate() >>> print output ('root:x:0:0:root:/root:/bin/bash\noperator:x:11:0:operator:/root:/sbin/nologin\n', None)
封装一个函数:功能是调用系统命令:
import subprocess def f1(cmd): a = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) output = a.stdout.read() code = a.wait() return code, output print f1('ls') print f1('lll') 输出结果: >>> print f1('ls') (0, 'tb.txt\ntest2.py\ntest.py\n') >>> print f1('lll') (127, '/bin/sh: lll: command not found\n')
本文名称:python调用Linux脚本或者shell指令的几种方法
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