實用 Linux 指令

記錄一些指令，方便之後快速回憶！

man command → manual page
- h - 秀出快捷鍵，像是要在視窗內 moving、searching、jumping，可以怎麼下
- /pattern - 往下找符合 pattern 的字串
  - n - 跳到下一個符合 pattern 的字串
  - N - 跳到上一個符合 pattern 的字串
- Enter - 往下移動一行
- Space - 往下移動一頁
- g - 移動到 manual page 的最上方
- G - 移動到 manual page 的最下方
- q - 離開 manual page
which python3 → /opt/homebrew/bin/python3
- which - locate a program file in the user’s path
mkdir -p newdir/product/reviews
- -p - Create intermediate directories as required.
chmod u=rwx,g+x,o= sales.data
- (1) ugoa - u for user, g for group, o for other, a for all.
- (2) +-= (3) rwx
chmod 754 file
- U → rwx → 111 → 7
- G → r-x → 101 → 5
- O → r– → 100 → 4
umask - a command that determines the settings of a mask that controls how file permissions are set for newly created files.
find [path...] [expression] - Recursively finds files in path that match expression.
- find . -name "Screen*" (-iname 會忽略大小寫)
- find . -ls - 對找到的檔案們進行 ls
- find . -mtime num_days - 找出所有 num_days-old 的檔案
  - find . -mtime +10 -mtime -13 - more than 10 days old, but less than 13 days old
- find . -size +500k -size -10M
- find . -newer file
- find . -exec command {} \; - Run command against all the files that are found.
  - find root_path -name '*.ext' -exec wc -l {} \; - Run a command for each file (use {} within the command to access the filename)
- find . -type d -newer b.txt - find directories that are newer than a given file
locate pattern - List files that match pattern.
- When you run locate it is simply querying the index or database created by updatedb and not looking at each file on the system.
- This is really, really fast.
- The down side is that the data is not in real time.
除了 diff 也有 sdiff 及 vimdiff
grep -v pattern file - Selected lines are those not matching any of the specified patterns.
- -v, –invert-match
The pipe (|) means take the standard output from the preceding command and pass it as the standard input to the following command.
Pipe Output to a Pager
- strings ~/Documents/test.mp3 | less
Redirection
- standard input → stdin → 0
- standard output → stdout → 1
- standard error → stderr → 2
- > - Redirects standard output to a file, overwriting (truncating) any existing contents of the file. If no file exists, it creates one. ls -lF /opt/apache > files.txt same as ls -lF /opt/apache 1> files.txt
- >> - Redirects standard output to a file and appends to any existing contents. If no file exists, it creates one. ls -lF /opt/apache >> files.txt
- < - Redirects input from a file to the command preceding the less-than sign. sort < files.txt same as sort 0< files.txt
- sort < files.txt > sorted_files.txt - The output of the sort command is then redirected to the sorted_files.txt file.
- & - Used with redirection to signal that a file descriptor is being used instead of a file name.
- 2>&1 - Combine standard error and standard output.
- 2> file - Redirect standard error to a file.
- ls here not-here 1> out 2> out.err
  - cat out → here
  - cat out.err → ls: not-here: No such file or directory
- ls here not-here > out.both 2>&1
  - cat out.both → ls: not-here: No such file or directory \n here
- ls here not-here > /dev/null 2>&1 - Redirect output to nowhere.
scp source destination - Copy source to destination.
- scp test.txt linuxsvr1:~/
echo 'export xxx="ooo"' >> ~/.bash_profile - To make your xxx persist between logins, add the value to your personal initialization files.
alias ll='ls -l' (add them to one of your personal initialization files, like .zshrc, to make them persist between sessions)
- You could create these shortcuts to help you feel more at home.
.zshrc 編輯完後可 source .zshrc，就不用得重開一個新的 terminal 才會有新的設定
history (可設定環境變數 HISTSIZE，值越大，保存越多 command history)
Tab Completion
Dealing with Long Shell Commands: The backslash (\) is the line continuation character.
printenv – print out the environment variables (env 也可以)
crontab - Schedule cron jobs to run on a time interval for the current user.