用Python寫運維指令碼時，經常需要執行linux shell的命令，Python中的commands模組專門用於呼叫Linux shell命令，並返回狀態和結果，下面是commands模組的3個主要函式：

1. commands.getoutput('shell command')

執行shell命令，返回結果（string型別）

>>> commands.getoutput('pwd')
'/home/oracle'

2. commands.getstatus('file')

該函式已被python丟棄，不建議使用，它返回 ls -ld file 的結果（String）(返回結果太奇怪了，難怪被丟棄）

>>> commands.getstatus('admin.tar')
'-rw-rw-r-- 1 oracle oracle 829440 Jan 29 10:36 admin.tar'

執行shell命令, 返回兩個元素的元組tuple(status, result)，status為int型別，result為string型別。

cmd的執行方式是{ cmd ; } 2>&1, 故返回結果包含標準輸出和標準錯誤.

>>> commands.getstatusoutput('pwd')
(0, '/home/oracle')
 

import commands

threshold = 10
flag = False

title=commands.getoutput("df -h|head -1")

'''
Check sda disk space usage like below format:
/dev/sda2              20G  2.3G   17G  13% /
/dev/sda6              20G  306M   19G   2% /var
/dev/sda3              49G  2.8G   44G   7% /home
/dev/sda5              49G  4.5G   42G  10% /opt
/dev/sda1             194M   12M  172M   7% /boot
'''

chkDiskList=commands.getoutput("df -h|grep sda").split('\n')
usedPercents=commands.getoutput("df -h|grep sda|awk '{print $5}'|grep -Eo '[0-9]+'").split('\n')

for i in range(0,len(usedPercents)):
  if int(usedPercents[i]) >= threshold:
    chkDiskList[i] += '    ----Caution!!! space usage >= ' + str(threshold)
    flag = True

'''
Check disk space usage like below format:
/dev/mapper/backup-backup_lv
                      751G   14G  699G   2% /backup
/dev/mapper/data-data_lv
                      751G  172G  540G  25% /data
'''      

        
chkDiskList_2=commands.getoutput("df -h|grep -v sda|grep -v tmp|grep -v system").split('\n')
usedPercents_2=commands.getoutput("df -h|grep -v map|grep -v sda|grep -v tmp|grep -v system|awk '{print $4}'|grep -Eo '[0-9]+'").split('\n')

for i in range(0,len(usedPercents_2)): 
  if int(usedPercents_2[i]) >= threshold:
    chkDiskList_2[i*2 + 1] += '    ----Caution!!! space usage >= ' + str(threshold)
    flag = True

if flag == True:
  #combine tile, chkDiskList, chkDisklist_2
  result = [title,]
  result.extend(chkDiskList)
  result.extend(chkDiskList_2)
  for line in result:
    print line
 

[oracle@lx200 ~/admin/python]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              20G  2.3G   17G  13% /
/dev/sda6              20G  306M   19G   2% /var
/dev/sda3              49G  2.8G   44G   7% /home
/dev/sda5              49G  4.5G   42G  10% /opt
/dev/sda1             194M   12M  172M   7% /boot
tmpfs                  18G     0   18G   0% /dev/shm
/dev/mapper/backup-backup_lv
                      751G   14G  699G   2% /backup
/dev/mapper/data-data_lv
                      751G  174G  539G  25% /data

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              20G  2.3G   17G  13% /    ----Caution!!! space usage >= 10
/dev/sda6              20G  306M   19G   2% /var
/dev/sda3              49G  2.8G   44G   7% /home
/dev/sda5              49G  4.5G   42G  10% /opt    ----Caution!!! space usage >= 10
/dev/sda1             194M   12M  172M   7% /boot
/dev/mapper/backup-backup_lv
                      751G   14G  699G   2% /backup
/dev/mapper/data-data_lv
                      751G  174G  539G  25% /data    ----Caution!!! space usage >= 10