1.如何调用该方法：
from fabric import context_managers
ps:上下文管理需要用with关键字启用：
如：
with context_managers.cd('/tmp'):
run(...)
这样才能保证是在该目录下操作。
2.方法：
（1）with context_managers.cd(一个目录的路径)：
指定进入一个目录，然后在该目录下执行操作。
例：
def cd(path):
with context_managers.cd(path):
run('touch a.txt')
在path的值的目录下创建一个a.txt文件。
（2）with context_managers.hide(['warnings','running','stdout','stderr','debug','everything']):
在hide中指定要隐藏的类型，warnings：警告、running：运行、stdout：标准输出、stderr：标准错误、debug:调试信息
#1.不适用hide
def no_hide(cmd):
run('echo nimei')
显示：
[192.168.1.219] Executing task 'no_hide'
[192.168.1.219] run: echo nimei
[192.168.1.219] Login password for 'root':
[192.168.1.219] out: nimei
[192.168.1.219] out:
Done.
Disconnecting from 192.168.1.219... done.
#2.running
def hide_running(cmd):
with context_managers.hide('running'):
run('echo nimei')
[192.168.1.219] Executing task 'running_hide'
[192.168.1.219] Login password for 'root': #此行本是[192.168.1.219] run: echo nimei，但被hide过滤掉了
#3.stdout
def stdout_hide(cmd):
with context_managers.hide('stdout'):
run(cmd)
显示
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f hide_test.py stdout_hide:'echo nimei'
[192.168.1.219] Executing task 'stdout_hide'
#这一行的[192.168.1.219] out: nimei和[192.168.1.219] out: 没有了，这就是过滤标准输出
(3)with context_managers.show('debug'):
这个方法和hide正相反，hide是掩藏，而show是显示，它的作用只是为了开启默认掩藏的debug模式。
(4)with context_managers.path(path,behavior='[append|prepend|replace]'):
这个方法类似于在系统中执行：export PATH=$PATH:path1:path2，是指定命令路径的。
而path方法除了传入一个path字符串参数以外，还要换入一个behavior=参数，参数有3个：
1.append添加在$PATH的最后
2.prepend添加在$PATH的最前方（个人认为，这个参数是为了让你写的执行文件不至于和系统命令重名，它会优先执行你的执行文件）
3.replace将$PATH中的内容清空，然后将你将的path变量赋给它
#脚本1：exec_file_echo.sh
##!/bin/bash
#echo nimei
#脚本2：ls
#echo nimei
#1.append
def append_path(path,exec_file):
with context_managers.path(path,behavior='append'):
run(exec_file)
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f path_test.py append_path:'/gyk_fab/','exec_file_echo.sh'
[192.168.1.219] Executing task 'append_path'
[192.168.1.219] run: exec_file_echo.sh
[192.168.1.219] Login password for 'root':
[192.168.1.219] out: nimei
[192.168.1.219] out:
Done.
Disconnecting from 192.168.1.219... done.
#2.prepend
def prepend_path(path,exec_file):
with context_managers.path(path,behavior='prepend'):
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f path_test.py prepend_path:'/gyk_fab/','ls'#ls本身不执行，而执行我写的ls脚本，这就是将路径添加在最前端的用处
[192.168.1.219] Executing task 'prepend_path'
[192.168.1.219] run: ls
Disconnecting from 192.168.1.219... done.
#replace
#范例1
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f path_test.py replace_path:'/gyk_fab/','which pwd'
[192.168.1.219] Executing task 'replace_path'
[192.168.1.219] run: which pwd
[192.168.1.219] out: /bin/bash: which: command not found
Fatal error: run() received nonzero return code 127 while executing!
Requested: which pwd
Executed: /bin/bash -l -c "export PATH=\"\"/gyk_fab/\"\" && which pwd"
Aborting.
run() received nonzero return code 127 while executing!
[root@salt-monion-1 gyk_fab]# which pwd
/bin/pwd
#范例2
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f path_test.py replace_path:'/gyk_fab/','ls'
[192.168.1.219] out: /gyk_fab/ls: line 4: find: command not found
Requested: ls
Executed: /bin/bash -l -c "export PATH=\"\"/gyk_fab/\"\" && ls"
[root@salt-monion-1 gyk_fab]# cat ls
#!/bin/bash
find / -name tmp
(5)with context_managers.prefix(系统命令):
该方法的作用和cmd1&&cmd2相同，就是当本命令执行成功后才能执行其他操作。
#!/bin/env python2.7
from fabric import context_managers
from fabric.operations import run
def no_prefix(prefix_cmd,run_cmd):
run(prefix_cmd)
run(run_cmd)
def prefix_test(prefix_cmd,run_cmd):
with context_managers.prefix(prefix_cmd):
run(run_cmd)
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f test_prefix.py prefix_test:'cd /tmp','ls'
[192.168.1.219] Executing task 'prefix_test'
[192.168.1.219] out: dir pip_build_root timer_creategFkcio.c yum.log yum_save_tx-2015-03-16-23-09uxAPw7.yumtx
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f test_prefix.py prefix_test:'cd tmp','ls'
[192.168.1.219] out: /bin/bash: line 0: cd: tmp: 没有那个文件或目录
Fatal error: run() received nonzero return code 1 while executing!
Executed: /bin/bash -l -c "cd tmp && ls"
run() received nonzero return code 1 while executing!
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f test_prefix.py no_prefix:'cd /tmp','ls'
[192.168.1.219] Executing task 'no_prefix'
[192.168.1.219] run: cd /tmp
[192.168.1.219] out: anaconda-ks.cfg install.log install.log.syslog
[root@salt-monion-1 gyk_fab]# fab -H 192.168.1.219 -f test_prefix.py no_prefix:'cd tmp','ls'
[192.168.1.219] run: cd tmp
Requested: cd tmp
Executed: /bin/bash -l -c "cd tmp"
(6)with context_managers.setting(env的key=env相应的值,...):
暂时（在with的作用域里），覆盖或更新任何提到的关键字的env变量的值，用env.键设置是全局变量，用这个可以设置局部变量。
范例暂时不写，等整理到env的时候在说。
(7)with context_managers.quiet():
它等同于with context_managers.settings(context_managers.hide('everything'),warn_only=True):
from fabric import colors
from fabric.api import env
env.hosts=['192.168.1.219']
def quiet_test(cmd):
with context_managers.quiet():
status=run(cmd)
if status.succeeded:
print colors.green('nimei')
[root@salt-monion-1 gyk_fab]# fab -f quiet_test.py quiet_test:'ls'
[192.168.1.219] Executing task 'quiet_test'
nimei
[root@salt-monion-1 gyk_fab]# fab -f quiet_test.py quiet_test:'lasdddd'
同功能代码：
env.password='659171'
def quiet_test(cmd): #context_managers.quiet()
def equest_quiet(cmd): #context_managers.settings()
with context_managers.settings(context_managers.hide('everything'),warn_only=True):
if status.succeeded :
else:
print colors.red('cao nimei')
[root@salt-monion-1 gyk_fab]# fab -f quiet_test.py equest_quiet:'lsaaa'
[192.168.1.219] Executing task 'equest_quiet'
cao nimei
[root@salt-monion-1 gyk_fab]# fab -f quiet_test.py equest_quiet:'ls'
(7)with context_managers.warn_only():
等同于context_mangers.setting(warn_only=True):
(8)context_managers.shell_env(键=值):
为shell命令设置环境变量。比如说安装ACE时需要制定ACE_HOME=安装包路径，这时候就可以使用shell_env
本文转自 msj0905 51CTO博客，原文链接:http://blog.51cto.com/sky66/1684901
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