Lecture 01 Shell

使用Windows的同学请先安装WSL或Linux虚拟机

Argument Parsing
参数间以空格分隔，第一个参数是命令，例如

❯ echo hello      world
hello world
❯ echo "hello       world"
hello       world

cd: 切换当前目录

❯ cd ~
❯ cd Fuyukawa/../././
# 还是在~，上面意味着先切换到（当前目录下的）Fuyukawa文件夹，
# 之后再cd ..之后再cd .等

一个命令就是一个program，当你输入一个命令时，shell会对$PATH变量中记录的路径逐个寻找，直到找到这个命令

❯ which date
/usr/bin/date
❯ /usr/bin/date
Sun Mar 29 20:29:07 CST 2026
❯ date
Sun Mar 29 20:29:08 CST 2026

which returns the pathnames of the files (or links) which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell.
It does this by searching the PATH for executable files matching the names of the arguments. It does not canonicalize path names.

grep 在文件中筛选

❯ cat test.txt
hello
world
你好
code
test.txt
test1
test2
test3
❯ grep "w" test.txt
world

❯ grep -r h .
./w2.txt:what
./w1.txt:hello
❯ find . -name "*.txt" -exec grep -l what {} \;
./w2.txt
# 在当前文件夹下找以.txt结尾的文件
# -exec是将找到的路径放入{}中并执行\;之前的命令
# 这里是执行grep -l what w1.txt
# 以及grep -l what w2.txt
# -l是打印出含有what的文件的路径

awk
sed

管道符 | 把左侧命令的输出作为右侧命令的输入