Shell学习笔记

地址操作

Code	全称	作用
pwd	print working directory	定位当前directory的位置
ls	listing	显示当前directory中的文件
.		当前位置
..		当前位置的上一级
~		当前用户主目录

文件操作

Code	全称	作用
cp	copy	拷贝文件
mv		* 移动文件 * 重命名文件
rm	remove	删除文件
rmdir		删除directory
mkdir		创建directory

数据操作

Code	全称	作用
cat	concatenate	连接文件或标准输入并打印它们
more
less		one page is displayed at a time
:n		move to the next file
:p		go back to the previous file
:q		quit
head		print the first few lines of a file (where "a few" means 10)
head -n 3		only display the first three lines of the file
ls -R		see everything underneath a directory, no matter how deeply nested it is
ls -R		prints a / after the name of every directory and a * after the name of every runnable program
man	manual	help to find out what commands do
cut
history		print a list of commands you have run recently
!55		re-run the 55th command in your history

• 按tab可以自动补全
• head and tail select rows, cut selects columns, and grep selects lines according to what they contain, and grep has the following command-line flags
  • -c: print a count of matching lines rather than the lines themselves
  • -h: do not print the names of files when searching multiple files
  • -i: ignore case (e.g., treat "Regression" and "regression" as matches)
  • -l: print the names of files that contain matches, not the matches
  • -n: print line numbers for matching lines
  • -v: invert the match, i.e., only show lines that don't match

Command-Line Flag

• -n: is meant to signal "number of lines"
• -R: means "recursive"
• -f: means "fields"
• -d: means "delimiter"

Combining Tools

Code	全称	作用
>		tell the shell to redirect the output to a file
wc	word count	print the number of characters, words, and lines in a file
sort		put data in order
uniq		remove adjacent duplicated lines

• The pipe symbol | tells the shell to use the output of the command on the left as the input to the command on the right.
• Ctrl+C: 终止程序进程

Wildcard

• *: match zero or more characters
• ? matches a single character, so 201?.txt will match 2017.txt or 2018.txt, but not 2017-01.txt.
• [...] matches any one of the characters inside the square brackets, so 201[78].txt matches 2017.txt or 2018.txt, but not 2016.txt.
• {...} matches any of the comma-separated patterns inside the curly brackets, so {*.txt, *.csv} matches any file whose name ends with .txt or .csv, but not files whose names end with .pdf.

[singh,johel]{*.pdf, *.txt} the expression in square brackets matches only one character, not entire words.
{singh.pdf, j*.txt} is ok.

Batch Processing

Code	全称	作用
set		get a complete list of the environment variables
echo		prints a variable's value's arguments

• To get the variable's value, you must put a dollar sign $ in front of it.

Loop

for …variable… in …list… ; do …body… ; done

Creating New Tools

How to edit a file

• Ctrl + K: delete a line.
• Ctrl + U: un-delete a line.
• Ctrl + O: save the file (O stands for 'output'). You will also need to press Enter to confirm the filename!
• Ctrl + X: exit the editor.