1.如何調用該方法：
from fabric import context_managers
ps:上下文管理需要用with關鍵字啟用：
如：
with context_managers.cd('/tmp'):
run(...)
這樣才能保證是在該目錄下操作。
2.方法：
（1）with context_managers.cd(一個目錄的路徑)：
指定進入一個目錄，然後在該目錄下執行操作。
例：
def cd(path):
with context_managers.cd(path):
run('touch a.txt')
在path的值的目錄下建立一個a.txt檔案。
（2）with context_managers.hide(['warnings','running','stdout','stderr','debug','everything']):
在hide中指定要隐藏的類型，warnings：警告、running：運作、stdout：标準輸出、stderr：标準錯誤、debug:調試資訊
#1.不适用hide
def no_hide(cmd):
run('echo nimei')
顯示：
[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過濾掉了
#3.stdout
def stdout_hide(cmd):
with context_managers.hide('stdout'):
run(cmd)
顯示
[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'
#這一行的[192.168.1.219] out: nimei和[192.168.1.219] out: 沒有了，這就是過濾标準輸出
(3)with context_managers.show('debug'):
這個方法和hide正相反，hide是掩藏，而show是顯示，它的作用隻是為了開啟預設掩藏的debug模式。
(4)with context_managers.path(path,behavior='[append|prepend|replace]'):
這個方法類似于在系統中執行：export PATH=$PATH:path1:path2，是指定指令路徑的。
而path方法除了傳入一個path字元串參數以外，還要換入一個behavior=參數，參數有3個：
1.append添加在$PATH的最後
2.prepend添加在$PATH的最前方（個人認為，這個參數是為了讓你寫的執行檔案不至于和系統指令重名，它會優先執行你的執行檔案）
3.replace将$PATH中的内容清空，然後将你将的path變量賦給它
#腳本1：exec_file_echo.sh
##!/bin/bash
#echo nimei
#腳本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本身不執行，而執行我寫的ls腳本，這就是将路徑添加在最前端的用處
[192.168.1.219] Executing task 'prepend_path'
[192.168.1.219] run: ls
Disconnecting from 192.168.1.219... done.
#replace
#範例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
#範例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(系統指令):
該方法的作用和cmd1&&cmd2相同，就是當本指令執行成功後才能執行其他操作。
#!/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: 沒有那個檔案或目錄
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相應的值,...):
暫時（在with的作用域裡），覆寫或更新任何提到的關鍵字的env變量的值，用env.鍵設定是全局變量，用這個可以設定局部變量。
範例暫時不寫，等整理到env的時候在說。
(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'
同功能代碼：
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(鍵=值):
為shell指令設定環境變量。比如說安裝ACE時需要制定ACE_HOME=安裝包路徑，這時候就可以使用shell_env
本文轉自 msj0905 51CTO部落格，原文連結:http://blog.51cto.com/sky66/1684901
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