经常使用命令行，比如 curl 测试接口响应时间

for i in {1..10};do curl -o /dev/null -s   -w "$i | time_namelookup: %{time_namelookup} | time_connect: %{time_connect} | time_starttransfer: %{time_starttransfer} | time_total: %{time_total}\n" "http://httpbin.org/ip";done

1 | time_namelookup: 0.016000 | time_connect: 0.016000 | time_starttransfer: 0.125000 | time_total: 0.141000
2 | time_namelookup: 0.016000 | time_connect: 0.016000 | time_starttransfer: 0.094000 | time_total: 0.109000
3 | time_namelookup: 0.016000 | time_connect: 0.031000 | time_starttransfer: 0.109000 | time_total: 0.109000
4 | time_namelookup: 0.015000 | time_connect: 0.031000 | time_starttransfer: 0.109000 | time_total: 0.109000
5 | time_namelookup: 0.031000 | time_connect: 0.031000 | time_starttransfer: 0.109000 | time_total: 0.109000
6 | time_namelookup: 0.016000 | time_connect: 0.016000 | time_starttransfer: 0.094000 | time_total: 0.109000
7 | time_namelookup: 0.016000 | time_connect: 0.016000 | time_starttransfer: 0.125000 | time_total: 0.125000
8 | time_namelookup: 0.000001 | time_connect: 0.016000 | time_starttransfer: 0.141000 | time_total: 0.141000
9 | time_namelookup: 0.015000 | time_connect: 0.015000 | time_starttransfer: 0.093000 | time_total: 0.109000
10 | time_namelookup: 0.000001 | time_connect: 0.015000 | time_starttransfer: 0.109000 | time_total: 0.125000

奈何命令行参数太多，记不住怎么办？这时候你需要个男人，它就是 man

man

#man curl 
curl(1)                                      Curl Manual                                     curl(1)

NAME
       curl - transfer a URL

SYNOPSIS
       curl [options] [URL...]

DESCRIPTION
       curl  is  a  tool  to transfer data from or to a server, using one of the supported protocols
       (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP,  LDAPS,  POP3,  POP3S,  RTMP,
       RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP).  The command is designed to work without user
       interaction.

       curl offers a busload of useful tricks like proxy support, user authentication,  FTP  upload,
       HTTP  post,  SSL  connections, cookies, file transfer resume, Metalink, and more. As you will
       see below, the number of features will make your head spin!

       curl is powered by libcurl for all transfer-related features. See libcurl(3) for details.

URL
       The URL syntax is protocol-dependent. You'll find a detailed description in RFC 3986.

       You can specify multiple URLs or parts of URLs by writing part sets within braces as in:

        http://site.{one,two,three}.com

       or you can get sequences of alphanumeric series by using [] as in:

        ftp://ftp.numericals.com/file[1-100].txt
        ftp://ftp.numericals.com/file[001-100].txt    (with leading zeros)
        ftp://ftp.letters.com/file[a-z].txt

男人的确很强悍，给出了这么多提示，但没有我真正想要的。。。还是不知道怎么用。

相信你在技术文章里经常会看到 TL;DR 即Too Long; Didn’t Read. 太长不看， man curl 的内容就是太长了，我不看。

就是这个更强壮的男人 tldr，它一个命令行工具，直接使用 npm install -g tldr 来安装。

tldr

[root@VM_0_14_centos ~]# npm install -g tldr
/usr/local/n/versions/node/11.4.0/bin/tldr -> /usr/local/n/versions/node/11.4.0/lib/node_modules/tldr/bin/tldr
+ tldr@3.2.7
added 113 packages from 103 contributors in 60.759s


   ╭───────────────────────────────────────────────────────────────╮
   │                                                               │
   │       New minor version of npm available! 6.4.1 → 6.9.0       │
   │   Changelog: https://github.com/npm/cli/releases/tag/v6.9.0   │
   │               Run npm install -g npm to update!               │
   │                                                               │
   ╰───────────────────────────────────────────────────────────────╯

安装完后先看看 tldr 自己怎么用吧。

$ tldr tldr

  tldr

  Simplified man pages.
  More information: .

  - Get typical usages of a command (hint: this is how you got here!):
    tldr command

  - Show the tar tldr page for linux:
    tldr -p linux tar

  - Get help for a git subcommand:
    tldr git checkout

小试牛刀下

$ tldr -p linux tar

  tar

  Archiving utility.
  Often combined with a compression method, such as gzip or bzip.
  More information: .

  - Create an archive from files:
    tar -cf target.tar file1 file2 file3

  - Create a gzipped archive:
    tar -czf target.tar.gz file1 file2 file3

  - Extract an archive in a target directory:
    tar -xf source.tar -C directory

  - Extract a gzipped archive in the current directory:
    tar -xzf source.tar.gz

  - Extract a bzipped archive in the current directory:
    tar -xjf source.tar.bz2

  - Create a compressed archive, using archive suffix to determine the compression program:
    tar -caf target.tar.xz file1 file2 file3

  - List the contents of a tar file:
    tar -tvf source.tar

  - Extract files matching a pattern:
    tar -xf source.tar --wildcards "*.html"

嗯，很简洁，直接给出了tar需要的参数，再来看curl

λ tldr curl

  curl

  Transfers data from or to a server.
  Supports most protocols, including HTTP, FTP, and POP3.

  - Download the contents of an URL to a file:
    curl http://example.com -o filename

  - Download a file, saving the output under the filename indicated by the URL:
    curl -O http://example.com/filename

  - Download a file, following [L]ocation redirects, and automatically [C]ontinuing (resuming) a previous file transfer:
    curl -O -L -C - http://example.com/filename

  - Send form-encoded data (POST request of type application/x-www-form-urlencoded):
    curl -d 'name=bob' http://example.com/form

  - Send a request with an extra header, using a custom HTTP method:
    curl -H 'X-My-Header: 123' -X PUT http://example.com

  - Send data in JSON format, specifying the appropriate content-type header:
    curl -d '{"name":"bob"}' -H 'Content-Type: application/json' http://example.com/users/1234

  - Pass a user name and password for server authentication:
    curl -u myusername:mypassword http://example.com

  - Pass client certificate and key for a resource, skipping certificate validation:
    curl --cert client.pem --key key.pem --insecure https://example.com

这个男人果然更强悍，常用的curl命令都包括了，我喜欢。

除了自带的命令，安装的命令也可以

[root@VM_0_14_centos ~]# tldr python

  python

  Python language interpreter.
  More information: https://www.python.org.

  - Call a Python interactive shell (REPL):
    python

  - Execute script in a given Python file:
    python script.py

  - Execute script as part of an interactive shell:
    python -i script.py

  - Execute a Python expression:
    python -c "expression"

  - Run library module as a script (terminates option list):
    python -m module arguments

  - Interactively debug a Python script:
    python -m pdb script.py

除了node 还有其他版本 https://github.com/tldr-pages/tldr 比如Python，直接pip install tldr安装

如果你不想安装tldr,也可以直接使用网页在线查看https://tldr.sh/

有了tldr,妈妈再也不用担心我记不住命令行参数了，还有没有比 tldr更强悍的男人呢，有，比如cheat https://github.com/cheat/cheat 直接使用pip install cheat安装。

cheat

看看 cheat 怎么用吧

$ cheat cheat
# To see example usage of a program:
cheat <command>

# To edit a cheatsheet
cheat -e <command>

# To list available cheatsheets
cheat -l

# To search available cheatsheets
cheat -s <command>

# To get the current `cheat' version
cheat -v

试试 curl

$ cheat curl
# Download a single file
curl http://path.to.the/file

# Download a file and specify a new filename
curl http://example.com/file.zip -o new_file.zip

# Download multiple files
curl -O URLOfFirstFile -O URLOfSecondFile

# Download all sequentially numbered files (1-24)
curl http://example.com/pic[1-24].jpg

# Download a file and pass HTTP Authentication
curl -u username:password URL

# Download a file with a Proxy
curl -x proxysever.server.com:PORT http://addressiwantto.access

# Download a file from FTP
curl -u username:password -O ftp://example.com/pub/file.zip

# Get an FTP directory listing
curl ftp://username:password@example.com

# Resume a previously failed download
curl -C - -o partial_file.zip http://example.com/file.zip

# Fetch only the HTTP headers from a response
curl -I http://example.com

# Fetch your external IP and network info as JSON
curl http://ifconfig.me/all/json

# Limit the rate of a download
curl --limit-rate 1000B -O http://path.to.the/file

# Get your global IP
curl httpbin.org/ip

# Get only the HTTP status code
curl -o /dev/null -w '%{http_code}\n' -s -I URL

$ cheat python
# Desc: Python is a high-level programming language.

# Basic example of server with python
# Will start a Web Server in the current directory on port 8000
# go to http://127.0.0.1:8000

# Python v2.7
python -m SimpleHTTPServer
# Python 3
python -m http.server 8000

# SMTP-Server for debugging, messages will be discarded, and printed on stdout.
python -m smtpd -n -c DebuggingServer localhost:1025

# Pretty print a json
python -mjson.tool

比tldr更详细，如果你也不想安装可以直接使用curl

cht.sh

[root@VM_0_14_centos ~]# curl cht.sh/curl
# Download a single file
curl http://path.to.the/file

# Download a file and specify a new filename
curl http://example.com/file.zip -o new_file.zip

# Download multiple files
curl -O URLOfFirstFile -O URLOfSecondFile

# Download all sequentially numbered files (1-24)
curl http://example.com/pic[1-24].jpg

# Download a file and follow redirects
curl -L http://example.com/file

# Download a file and pass HTTP Authentication
curl -u username:password URL

# Download a file with a Proxy
curl -x proxysever.server.com:PORT http://addressiwantto.access

# Download a file from FTP
curl -u username:password -O ftp://example.com/pub/file.zip

# Get an FTP directory listing
curl ftp://username:password@example.com

# Resume a previously failed download
curl -C - -o partial_file.zip http://example.com/file.zip

# Fetch only the HTTP headers from a response
curl -I http://example.com

# Fetch your external IP and network info as JSON
curl http://ifconfig.me/all/json

# Limit the rate of a download
curl --limit-rate 1000B -O http://path.to.the/file

# POST to a form
curl -F "name=user" -F "password=test" http://example.com

# POST JSON Data
curl -H "Content-Type: application/json" -X POST -d '{"user":"bob","pass":"123"}' http://example.com

# POST data from the standard in / share data on sprunge.us
curl -F 'sprunge=<-' sprunge.us

看看Python的requests怎么用

[root@VM_0_14_centos ~]# curl cheat.sh/python/requests
#  python-requests: Limit Number of Redirects Followed
#
#  You have to create Session (http://www.python-
#  requests.org/en/latest/api/requests.Session) object and set
#  max_redirects variable to 3

session = requests.Session()
session.max_redirects = 3
session.get(url)

#  TooManyRedirects exception will be raised if a requests exceeds
#  maximum number of redirects.
#
#  Related github issue discussing why you can not set max_redirects per
#  request https://github.com/kennethreitz/requests/issues/1300
#
#  [Alik] [so/q/31552627] [cc by-sa 3.0]