# AWK and Python CODE 對比
## Example 1 Read Special Field from File
## 範例1從檔案讀取特定欄位

##### Awk Code {#awk-code}

awk  -F: '{ print $1 } ' /etc/passwd

##### Python code {#python-code}

import os 

#first step to open File 
with open('/etc/passwd' , 'r') as passfile:
#second step using loop to read each line.  
    for line in passfile:
#third step to read special filed from pass 
        line.split(':')[0]  #as awk -F:
        #But in python first position is 0 not 1

---

## Example 2 Read special Number of rows from file
## 範例2 在檔案中讀取特定行數的的資料
##### Awk Code {#awk-code-example3}

awk -F: 'NR==1 {print $1 } ' /etc/passwd

#### Python Code {#python-code-example2}

import os
row=2
#first step to open File 
with open('/etc/passwd' , 'r') as passfile:
#second step using loop to read each line.  
    for idx,lines in enumerate(passfile):
#third step to read special filed from pass
        if idx == row:
            print(lines.split(':')[0] )

---

## Example3 list length greate special size
## 列出長度大於某個數值的row
##### Awk Code {#awk-code_1}

awk 'length > 72' /etc/passwd

##### Python code {#python-code_1}

import os
rowlength=72
#first step to open File 
with open('/etc/passwd' , 'r') as passfile:
#second step using loop to read each line.  
    for line in passfile:
        if line.legth() > rowlength:
            print(line)

---

## Example 4 print each line length from file {#example-4-print-each-line-length-from-file}
## 列出每一行的長度
#### Awk code

awk '{print length($2)}'  /etc/passwd

#### Python code

import os
row=2
#first step to open File 
with open('/etc/passwd' , 'r') as passfile:
#second step using loop to read each line.  
    #for idx,lines in enumerate(passfile):
    for line in passfile:
#third step to read special filed from pass
        print(len(line.split(':')[0]))
#as awk -F:
        #But in python first position is 0 not 1  th

---

## Example 5 Revese Order {#example-5-revese-order}
## 將資料作反序
#### Awk code

awk -F: '{ for (i = NF; i > 0; --i) print $i }'  /etc/passwd

#### Python code

Reference from :

[Python And C compare](http://www.saltycrane.com/blog/2009/04/how-reverse-words-sentence-using-python-and-c/)

import os 
#first step to open File 
with open('/etc/passwd' , 'r') as passfile:
    for line in passfile:
    #Split word string and use reversed func 
    #after split() word is list type not string. 
        word=line.split(':')
        result=" ".join(reversed(word))
        print(result)

---

## Example 6 Using Awk to summary a field from all line.
## 作SUMMARY
#### Awk code

awk -F: '{s += $4} END { print "sum is ", s }' /etc/passwd

#### Python code

import os 
sum=0
with open('/etc/passwd' , 'r') as passfile:
#second step using loop to read each line.  
    for line in passfile:
        i =line.split(':')[3]
        sum = sum + int(i)

        print(sum)

Example 7 Using Regex to search a string in the file

### Awk Code

awk -F: '$1 ~ /^ro*t/ { print $1 } ' /etc/passwd

root

### Python code

import os 
import re 

#depond , if you need to many time search and compare using compile
findaccount=re.compile(r'^ro*')
#first step to open File

with open('/etc/passwd' , 'r') as passfile:
#second step to read each line and to do pattern match 
#if match show first field
    for line in passfile:


        result=findaccount.match(line)
        if result:
            print(line.split(':')[0]
        else:
            pass

---

# EXAMPLE 8

## Awk Code

awk -F: '{sum[$7]++}END{for(i in sum)print sum[i],i}'  /etc/passwd

Result:
1  
1  /bin/sync
2  /bin/bash
2  /sbin/nologin
26  /bin/false
17  /usr/sbin/nologin

### Python code

import os
#first step to open File

with open('/etc/passwd' , 'r') as passfile:
    counter=Counter()
    for line in passfile:
        field=line.split(':')[6]
        #print(field)
        counter[field] += 1
#print(help(counter))
for item in counter:
    print('{0},{1}'.format(item,counter[item]))

Result:

/bin/false
,26
/usr/sbin/nologin
,17
/bin/sync
,1
/bin/bash
,2
/sbin/nologin
,2

,

# Example9

用於去抓出一個檔案比對出來的行及下一行然後直接放進一個List 中

import os
import re
import itertools
file='mobile-142.txt'

def create_list_of_match(file,searchstr):
    alias_index=[]
    with open(file, 'r') as f :

         for line_index, line in enumerate(f):
             result=re.findall(searchstr,line)
             if result:
                 #print(line_index)
                 alias_index.append(line_index)
    return alias_index



def seekfile(file,location):
    with open(file,'r') as f:
        for  i, line in  enumerate(f):
            if location==i:
                print(line)
                return line
def seekfile_and_offset(file,location,offset):
    with open(file,'r') as f:
        #current=f.readlines()[location]
        #nextone=f.readlines()[location+offset]
        content_list=[]
        location2=location+offset
        for  i, line in  enumerate(f):
            if location==i:
                content_list.append(line.strip())
            elif location2==i:
                content_list.append(line.strip())
        return content_list


list=create_list_of_match(file,'alias')
for x in list:
    print(seekfile_and_offset(file,x,1))

# Example10

Usage : if and else

查出一個PATTERN 然後作比較

awk -F: '/^root/{if($3==1){print "OK"  } else {print "error"} } ' /etc/passwd
error

Example 11

找出不固定位置的特定字元

awk '/cs1/ {for(i=1;i<=NF;i++) { if ($i~/^cs1/ ) { print $i } } }' ./ns.log.0