Change strings in vi or vim.


Environment and Prerequisite

  • Linux base system
  • Bash shell(/bin/bash)
  • vi or vim


vi(or vim) string replacement

Basic Form

Format

:%s/[original string]/[string to replace]/[options]
  • Use above form with various options.
  • Options can be used in multiple.
  • If omit % in above command, only current cursor line string will be replaced.

Options

  • g : Replace all matched strings(not only first occurrence in each line).
ThisThisThis -> testtesttest
:%s/This/test/g
  • c : Check before replacement.
ThisThisThis -> testThisThis
~
replace with test (y/n/a/q/l/^E/^Y)?y
:%s/This/test/c
  • i : Don’t care upper and lower case.
ThistHisthIs -> testtesttest
:%s/This/test/ig


Examples

  • Make test text file.
$ vi test.txt
This is test string. This is it!
This is second string.

Example 0 - Replace first ‘This’ to ‘tHIS’ in current line

  • Just remove % like below.
tHIS is test string. This is it!
This is second string.
~
~
:s/This/tHIS

Example 1 - Replace first ‘This’ to ‘tHIS’ in each line

  • If there is no option, replace string in one line and move to next line. So, it moves to next line even though there are more matched strings after replacement.
tHIS is test string. This is it!
tHIS is second string.
~
~
:%s/This/tHIS

Example 2 - Replace all ‘This’ to ‘tHIS’

  • Replace all matched strings using g option.
tHIS is test string. tHIS is it!
tHIS is second string.
~
~
:%s/This/tHIS/g

Example 3 - Check every time when replacing

  • Check every time by using c option.
  • Use g option to replace all matched strings.
  • Current example give input in y->n->y order.
this is test string. This is it!
this is second string.
~
~
replace with test (y/n/a/q/l/^E/^Y)?y
:%s/This/tHIS/cg

Example 4 - Replace ‘This’ to ‘tHIS’ while ignoring upper and lower case

  • Use i option to ignore upper and lower case.
  • Use g option to replace all matched strings.
tHIS is test string. tHIS is it!
tHIS is second string.
~
~
:%s/this/tHIS/ig


Reference

pdb를 이용해 python 코드를 디버깅하는 방법을 알아보자.


환경

  • Linux 기반 시스템
  • Bash shell(/bin/bash)
  • Python


pdb

pdb란?

  • pdb : 파이썬 디버깅 도구로 파인썬 인터프리터를 줄마다 보면서 실행할 수 있도록 도와주는 도구입니다.


실행 방법

pdb 실행방법 - 1

  • 처음부터 코드를 실행할 때 사용
python3 -m pdb example.py
  • 실행 예제
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb)

pdb 실행방법 - 2

  • 코드의 특정 부분부터 사용
# In python code
...
import pdb; pdb.set_trace()
...
  • 실행 예제
$ python test.py
> /Users/taewoo/test.py(6)<module>()
-> b=30
(Pdb)


사용법

사용 명령어 목록

  • l : 주변 소스코드들을 출력하며 현재 라인이 화살표로 나옵니다.
  • n : 다음 문장으로 이동합니다. 즉, 위에 l에서 위치한 부분을 실행하고 다음 명령어줄로 가는겁니다.
  • s : 흔히 사용하는 ‘Step Into’로 함수 내부로 들어갑니다. --Call--이라고 나오며 다 진행된 후에는 --Return--이 나옵니다.
  • c : 다음줄부터 중단점을 만날때까지 코드를 실행하며 중단점이 없다면 끝까지 실행합니다.
  • r : 현재 함수의 return이 나올때까지 실행합니다.
  • w : 함수의 call stack을 보여줍니다.
  • cl : 모든 중단점들을 삭제합니다.
  • b : 특정파일이나 패키지의 줄번호나 함수명으로 중단점을 만들 수 있습니다.
  • a : 현재 함수의 매개변수들을 출력.

사용 명령어 예제

  • l : 주변 소스코드들을 출력하며 현재 라인이 화살표로 나옵니다.
(Pdb) l
  1  	def test_sum(a,b):
  2  	    return a+b
  3
  4  	a=10
  5  ->	b=30
  6  	c=test_sum(a,b)
  7
  8  	for i in range(1,10):
  9  	    a = a + i
 10
 11  	import requests
  • n : 다음 문장으로 이동합니다. 즉, 위에 l에서 위치한 부분을 실행하고 다음 명령어줄로 가는겁니다.
(Pdb)  n
> /Users/taewoo/test.py(6)<module>()
-> c=test_sum(a,b)
  • s : 흔히 사용하는 ‘Step Into’로 함수 내부로 들어갑니다. --Call--이라고 나오며 다 진행된 후에는 --Return--이 나옵니다.
(Pdb)  s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
...
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • c : 다음줄부터 중단점을 만날때까지 코드를 실행하며 중단점이 없다면 끝까지 실행합니다.
(Pdb) c
The program finished and will be restarted
  • r : 현재 함수의 return이 나올때까지 실행합니다.
(Pdb) s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) r
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • w : 함수의 call stack을 보여줍니다.
(Pdb) w
  /Users/taewoo/.pyenv/versions/3.6.2/lib/python3.6/bdb.py(431)run()
-> exec(cmd, globals, locals)
  <string>(1)<module>()
  /Users/taewoo/test.py(9)<module>()
-> c=test_sum(a,b)
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • cl : 모든 중단점들을 삭제합니다.
(Pdb) cl
Clear all breaks? y
  • b : 특정파일이나 패키지의 줄번호나 함수명으로 중단점을 만들 수 있습니다.
(Pdb) b 8
Breakpoint 1 at /Users/taewoo/test.py:8
(Pdb) b test_sum
Breakpoint 2 at /Users/taewoo/test.py:1
# Stop at line number 8
(Pdb) c
> /Users/taewoo/test.py(8)<module>()
-> b=30
# Stop at function
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) b
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /Users/taewoo/test.py:8
	breakpoint already hit 2 times
2   breakpoint   keep yes   at /Users/taewoo/test.py:1
	breakpoint already hit 1 time
  • a : 현재 함수의 매개변수들을 출력.
(Pdb)  s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) a
a = 10
b = 30

기타

  • 변수 값을 확인하고 싶을때 해당 변수를 명령어처럼 입력하던가 print함수를 이용할 수 있습니다.
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) n
> /Users/taewoo/test.py(3)test_sum()
-> tmp=2
(Pdb) tmp
1
(Pdb) print(tmp)
1
(Pdb) type(data)
<class 'dict'>
(Pdb) data
{'data': [{'type': 'articles', 'id': '1', 'attributes': {'title': 'JSON API paints my bikeshed!', 'body': 'The shortest article. Ever.', 'created': '2015-05-22T14:56:29.000Z', 'updated': '2015-05-22T14:56:28.000Z'}, 'relationships': {'author': {'data': {'id': '42', 'type': 'people'}}}}], 'included': [{'type': 'people', 'id': '42', 'attributes': {'name': 'John', 'age': 80, 'gender': 'male'}}]}
  • 코드 상에 중단점 추가하기
  • 코드 중간에 import pdb; pdb.set_trace()를 추가하면 해당 부분에서 멈춥니다.
def test_sum(a,b):
    tmp=1
    tmp=2
    tmp=3
    return a+b

a=10
b=30
c=test_sum(a,b)

for i in range(1,10):
    a = a + i

import requests
import pdb; pdb.set_trace()
url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'

data = requests.get(url).json()
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb) c
> /Users/taewoo/test.py(16)<module>()
-> url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'
(Pdb)


참고자료

Debug python code using pdb.


Environment and Prerequisite

  • Linux base system
  • Bash shell(/bin/bash)
  • Python


pdb

What is pdb?

  • pdb : Interactive source code debugger for Python programs.


How to run

pdb run method - 1

  • Run pdb in start time.
python3 -m pdb example.py
  • Run example
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb)

pdb run method - 2

  • Add to code
# In python code
...
import pdb; pdb.set_trace()
...
  • Run example
$ python test.py
> /Users/taewoo/test.py(6)<module>()
-> b=30
(Pdb)


Usage

Usage command list

  • l : Print codes of around current point. Current point will be marked by arrow.
  • n : Move to next statement. In other words, run statement which is shown in above l command’s arrow and move to next statement.
  • s : Commonly used ‘Step Into’ command. --Call-- will be shown after stepped in and --Return-- will be shown after return.
  • c : Run codes until meet next break point.
  • r : Run command until meet return.
  • w : Show current call stack.
  • cl : Clear all break points.
  • b : Make break point to file’s or package’s specific function or line.
  • a : Print function’s all arguments.

Usage command example

  • l : Print codes of around current point. Current point will be marked by arrow.
(Pdb) l
  1  	def test_sum(a,b):
  2  	    return a+b
  3
  4  	a=10
  5  ->	b=30
  6  	c=test_sum(a,b)
  7
  8  	for i in range(1,10):
  9  	    a = a + i
 10
 11  	import requests
  • n : Move to next statement. In other words, run statement which is shown in above l command’s arrow and move to next statement.
(Pdb)  n
> /Users/taewoo/test.py(6)<module>()
-> c=test_sum(a,b)
  • s : Commonly used ‘Step Into’ command. --Call-- will be shown after stepped in and --Return-- will be shown after return.
(Pdb)  s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
...
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • c : Run codes until meet next break point.
(Pdb) c
The program finished and will be restarted
  • r : Run command until meet return.
(Pdb) s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) r
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • w : Show current call stack.
(Pdb) w
  /Users/taewoo/.pyenv/versions/3.6.2/lib/python3.6/bdb.py(431)run()
-> exec(cmd, globals, locals)
  <string>(1)<module>()
  /Users/taewoo/test.py(9)<module>()
-> c=test_sum(a,b)
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
  • cl : Clear all break points.
(Pdb) cl
Clear all breaks? y
  • b : Make break point to file’s or package’s specific function or line.
(Pdb) b 8
Breakpoint 1 at /Users/taewoo/test.py:8
(Pdb) b test_sum
Breakpoint 2 at /Users/taewoo/test.py:1
# Stop at line number 8
(Pdb) c
> /Users/taewoo/test.py(8)<module>()
-> b=30
# Stop at function
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) b
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /Users/taewoo/test.py:8
	breakpoint already hit 2 times
2   breakpoint   keep yes   at /Users/taewoo/test.py:1
	breakpoint already hit 1 time
  • a : Print function’s all arguments.
(Pdb)  s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) a
a = 10
b = 30

Others

  • We can check value of variable using print function or just type it to pdb.
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) n
> /Users/taewoo/test.py(3)test_sum()
-> tmp=2
(Pdb) tmp
1
(Pdb) print(tmp)
1
(Pdb) type(data)
<class 'dict'>
(Pdb) data
{'data': [{'type': 'articles', 'id': '1', 'attributes': {'title': 'JSON API paints my bikeshed!', 'body': 'The shortest article. Ever.', 'created': '2015-05-22T14:56:29.000Z', 'updated': '2015-05-22T14:56:28.000Z'}, 'relationships': {'author': {'data': {'id': '42', 'type': 'people'}}}}], 'included': [{'type': 'people', 'id': '42', 'attributes': {'name': 'John', 'age': 80, 'gender': 'male'}}]}
  • Add break point in code.
  • Pdb will be stopped on import pdb; pdb.set_trace()
def test_sum(a,b):
    tmp=1
    tmp=2
    tmp=3
    return a+b

a=10
b=30
c=test_sum(a,b)

for i in range(1,10):
    a = a + i

import requests
import pdb; pdb.set_trace()
url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'

data = requests.get(url).json()
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb) c
> /Users/taewoo/test.py(16)<module>()
-> url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'
(Pdb)


Reference

stderr를 /dev/null과 리다이렉트(Redirect)를 이용해 터미널 프롬프트 화면에 출력되지 않도록 해보자.


환경

  • Linux 기반 시스템
  • Bash shell(/bin/bash)
  • 리다이렉트(Redirect)


용어 정리

/dev/null이란?

  • /dev/null : NULL 장치라 불리는 부분으로 여기에 쓰여진 모든 값들을 버리지만 OS에는 작업에 성공했다고 보고하는 파일이다.
  • stderr/dev/null에 쓰면 표준 오류를 화면에서 안 볼 수 있다.

리다이렉트(Redirect)란?

  • Redirect('>'): 프로그램의 결과 혹은 출력(output)을 파일이나 다른 스트림으로 전달하거나 남길 때 사용하는 명령어다.
  • 참고 링크 : Redirect와 Pipe의 차이


사용 예제

find 명령어에서 stderr 무시하기

  • 기존에 출력되는 stderrPermission denied라고 나온다.
$ find / | grep neutron
find: ‘/run/docker’: Permission denied
find: ‘/run/containerd’: Permission denied
find: ‘/run/lxcfs’: Permission denied
find: ‘/run/sudo’: Permission denied
find: ‘/run/log/journal/50739525d1fb4eac9e863478fb990fed’: Permission denied
find: ‘/run/lvm’: Permission denied
  • /dev/nullstderr를 리다이렉트하니 Permission denied가 나오지 않는다.
  • 2stderr를 의미합니다.
find / 2> /dev/null | grep neutron
/home/twpower/test/neutron_patched
/home/twpower/test/neutron_patched/LICENSE
/home/twpower/test/neutron_patched/.gitignore
/home/twpower/test/neutron_patched/bin
...


참고자료

Redirect stderr to /dev/null so that ignore prints of standard errors in terminal prompt.


Environment and Prerequisite

  • Linux base system
  • Bash shell(/bin/bash)
  • Redirect


Terms

What is /dev/null?

  • /dev/null : Device file that discards all data written to it but reports that the write operation succeeded.
  • You can ignore standard error on screen when you write stderr to /dev/null.

What is redirect?

  • Redirect('>'): Redirect standard streams to user-specified locations like file or other stream.
  • Reference : Redirection (computing)


Usage example

Ignore stderr in find command

  • It prints Permission denied as stderr
$ find / | grep neutron
find: ‘/run/docker’: Permission denied
find: ‘/run/containerd’: Permission denied
find: ‘/run/lxcfs’: Permission denied
find: ‘/run/sudo’: Permission denied
find: ‘/run/log/journal/50739525d1fb4eac9e863478fb990fed’: Permission denied
find: ‘/run/lvm’: Permission denied
  • After redirect stderr to /dev/null, there is no Permission denied
  • 2 represents stderr
find / 2> /dev/null | grep neutron
/home/twpower/test/neutron_patched
/home/twpower/test/neutron_patched/LICENSE
/home/twpower/test/neutron_patched/.gitignore
/home/twpower/test/neutron_patched/bin
...


Reference