Linux Shell 명령어 정리

Path - Bash 환경설정

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• $PATH=$PATH:. → .추가 (.은 현재 작업 디렉토리) 하면 ./myprog 대신 myprog 로 실행 가능
• 자신의 홈디렉토리의 .bahs_profile을 수정
  • 'PATH=$PATH:$HOME/bin' 부분에서 : 으로 구분하여 덧붙이면 된다.

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CTRL 조합 명령

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• Ctrl + c : 프로세스의 종료
• Ctrl + d : 입력의 끝
• Ctrl + g : Bell (삑 소리)
• Ctrl + h : 백스페이스 (backspace)
• Ctrl + u : 입력줄을 지움
• Ctrl + z : 포그라운드 작업을 잠시 멈충

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Startup files

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• Script starting with .(dot) - ends with rc ("run command" —optional)
• look for scripts before (or after) execution
• usually they are for environment variable
• each command knows its own startup file names (try ls -a)
• bash (.bash_profile / .bashrc / .bash_logout ) : initialization for login shell for per-interactive shell, login shell clean-up file
• sh (.profile)
• vi (.exrc) : editor options
• mail (.mailrc) : mail options
• startx (.xinitrc) : x11 environment

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Redirection

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• Output redirection (>) : 프로세스의 출력을 새로운 파일을 생성해서 기록
• Output redirection (>>) : 프로세스의 출력을 지정한 파일의 마지막 부분에 추가
• Input redirecion (<) : 프로세스의 입력으로 파일을 사용

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Process / task / job

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• process : A process is an active entity, which requires a set of resources
• task : A task represents the execution of a single process or multiple processes on a compute node
• job : A collection of tasks that is used to perform a computation is known as job (batch jobs..)

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Multitasking

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• Foreground : current task (Command Running at the $ prompt)
• Background : Command running behind the scenes (not interactive → e.g text editor..)
  • An & sign at end of a simple command, pipeline, sequence of pipelines, a group of commands
  • Starts a sub-shell (commands are executed as a background process, does not take control of the keyboard)
  • A process id is displayed when it begins
  • Redirect the output to a file (if desired) → prevents background output on terminal
  • Background process cannot read from standard input, if they attempt to read from standard input, they terminate
• Every command is assigned a unique number (Process id - pid)
• **ps :** display currently running tasks
  • -a : all user processes
  • -u : user info
  • -x : not attached to a terminal
  • -e : ps to include all running processes
  • -f : ps to generate a full listing
  • -l : long listing
  • Column Meaning
    • S : the process state
    • UID : the effective user id of the process
    • PID : the process id
    • PPID : the parent process id
    • C : the percentage of CPU time that the process used in the last minute
    • PRI : the priority of the process
    • SZ : the size of the process's data and stack in kb
    • STIME : the time the process was created
    • TTY : the controlling terminal
    • TIME : the amount of CPU
    • CMD : The name of the command

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Kill Command

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• kill [-9] Pid1 Pid2...
  • Stop (kill) a currently running process → 프로세스를 강제 종료하는 경우 사용
  • can only stop proceases
  • -9 : sure kill (signal 번호로 9번 - 강제종료 를 가장 많이 사용함)
  • kill -9 <PID of mytest> → mytest를 강제 종료

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Job control

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• Foreground job
  • 명령어 라인을 실행시키거나 작업을 실행시키면 작업이 종료될 때까지 블록 상태가 되어 더이상 명령을 수행할 수 없는 상태
  • fg 명령어로 Background job을 Foreground job으로 바꿀 수 있음
• Background job
  • 새로운 프로세스를 할당받아 작업을 실행시키고 사용자는 터미널에서 계속 다른 작업을 할 수 있는 상태
  • bg 명령어로 Foreground job 혹은 Suspended job을 Background job으로 바꿀 수 있음
• jobs : List background jobs
• kill %(n) : Kill background job n
• wait : allows the shell to wait for one of its child processes to
• **sleep (n)** : suspend execution for an interval (지정된 시간 n초 동안 실행을 일시 중지, 주로 쉘 스크립트에서 많이 사용)
• **alias <명령어>="<별명>"** : 명령어에 다른 이름을 부여 (별명)
  • unalias <명령어> 명령으로 이미 설정되어 있는 별명을 해제
  • 별명을 작성할 때 명령어에 공백이 포함되면 "" 안에 기술해야 함
  • 로그아웃 시 정의가 무효되기 때문에 보통 로그인 설정 파일에 설정하는 경우가 많음
  • alias rm="rm -i" → rm을 rm -i 의 별명으로 지정

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Shell Command

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find [patname] [criteria]

• Where actions
  • To include the pathname of the file that's just been found in command, use the special symbol {}
  • command must end with a ;
  • -exec : Executes command
  • -ok : the interactive version of —exec
• $ find startingDir searchOptions commandToPerform
  • $ find . -name '*.c' -print
  • $ find .-mtime -14 -ls
  • $ find .-name'*.txt'-print
  • $ find / -size 0 -exec rm -i {} \;
  • $ find / -name'*.swp' -ok mv {} /tmp ';'

Filter Commands

• Filter manipulates the input, and then sends the results to the standard output stream
• Common filter commands
  • more, cat, cmp, cut, diff, head, tail, paste, sort, tr, uniq, wc, grep, sed, awk,...
• Cat [options] [input files]
  • Concatenating files
  • -e : print $ at end of line
  • -n : number lines
  • -s : silent (no error messages)
  • -t : print tabs and form feeds
  • -u : unbuffered output
  • -v : print control characters
  • cat file1 file2 → using cat to combine
  • cat file1 → Displaying a file with cat
  • cat > file1 → creating a file with cat (> : input from keyboard)
• head [options] [input files]
  • -N : number of lines
• tail [options] [input file]
  • +N : Skip N-1 lines
  • -N : N lines from end
  • -l : measured by lines (default)
  • -c : meaured by characters
  • -b : measured by blocks
  • -r : output in reverse order
• cut [options] [file list]
  • -c : character
  • -f : field
  • -d : delimeter
  • -s : suppress
• sort [options] [field specifiers] [input files]
  • -c : check sequence
  • -t : alternatie delimeter
  • -n : numeric sort
  • -m : merge (not sort)
  • -u : unique keys
  • -f : fold
  • -r : reverse
  • -b : ignore leading blanks
  • -d : dictionary sort
  • sort by fields : fields within a line
    • when the data that control the data sequence are not at the beginning of the line, we need a field sort
    • the UNIX sort defines a field as a set of characters delimeted by a single blank of a tab
  • $ sort -k 3 data.txt
  • $ sort -k 2,3 data.txt
  • $ sort -k 3.3 data.txt
• uniq [options] [input file]
  • -u : only nonrepeated lines output
  • -d : only repeated lines output
  • -c : add count to lines
  • -f : field
  • -s : character
• wc [options] [input files]
  • -c : character count
  • -l : line count
  • -w : word count
• cmp [options] file1 file2
  • -l : list
  • -s : suppress list
• diff [options] files or directories
  • -b : ignore trailing blanks
  • -w : ignore whitespace
  • -i : ignore case
  • < 는 원래 파일, > 는 바뀐 파일
  • 5c5,8 → 원래 파일에서 5 line이 바뀐 파일에서 5~8번째 line 으로 내용이 변경되었다는 의미
• Pipeline |
  • $ ps -ef | more
  • $ ps -ef | sort -k 2
  • $ ps -ef | sort -k 2 | head -5