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쉘프로그래밍강좌013: env로 쉘변수에 값 할당하여 변수리스트 출력하기

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쉘프로그래밍강좌013: env로 쉘변수에 값 할당하여 변수리스트 출력하기

 

 

 

 

 

env는 쉘변수 리스트를 확인하는 용도로 주로 사용됩니다.

 

 

 

 하지만, env를 이용하여 쉘변수에 새로운 값을 할당하거나 변경할 수 있다는 것을 알고 계신분들은 많지 않습니다.

 

 

 

 

 

예를 들어 HISTSIZE라는 변수에는 사용자가 사용한 명령어를 저장할 때에 몇 개까지 저장할 것인가를 결정하는 숫자가 저장되어 있습니다.

 

 

 

 아래 예를 보시는 바와 같이 기본값으로는 1000이라는 값이 저장되어 있습니다.

 

 

 

 

 

[root@RockyLinux01 ~]# echo $HISTSIZE

1000

[root@RockyLinux01 ~]#

 

그리고 다음 예와 같이 env를 이용하여 HISTSIZE라는 변수에 2000이라는 값을 할당하여 출력하고 있습니다.

 

 

 

 

 

[root@RockyLinux01 ~]# env HISTSIZE=2000

SHELL=/bin/bash

HISTCONTROL=ignoredups

HISTSIZE=2000

HOSTNAME=RockyLinux01

GUESTFISH_OUTPUT=\e[0m

PWD=/root

LOGNAME=root

XDG_SESSION_TYPE=tty

MODULESHOME=/usr/share/Modules

MANPATH=/usr/share/man:

GUESTFISH_RESTORE=\e[0m

MOTD_SHOWN=pam

HOME=/root

LANG=ko_KR.UTF-8

LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.webp=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.m4a=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.oga=01;36:*.opus=01;36:*.spx=01;36:*.xspf=01;36:

GUESTFISH_PS1=\[\e[1;32m\]><fs>\[\e[0;31m\]

SSH_CONNECTION=192.168.19.111 52828 192.168.19.201 22

XDG_SESSION_CLASS=user

TERM=xterm

LESSOPEN=||/usr/bin/lesspipe.sh %s

USER=root

MODULES_RUN_QUARANTINE=LD_LIBRARY_PATH LD_PRELOAD

LOADEDMODULES=

SHLVL=3

GUESTFISH_INIT=\e[1;34m

XDG_SESSION_ID=2

XDG_RUNTIME_DIR=/run/user/0

SSH_CLIENT=192.168.19.111 52828 22

DEBUGINFOD_URLS=https://debuginfod.centos.org/

which_declare=declare -f

XDG_DATA_DIRS=/root/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share

PATH=/root/.local/bin:/root/bin:/usr/share/Modules/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

MODULEPATH=/etc/scl/modulefiles:/etc/scl/modulefiles:/etc/scl/modulefiles:/usr/share/Modules/modulefiles:/etc/modulefiles:/usr/share/modulefiles

DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus

MAIL=/var/spool/mail/root

SSH_TTY=/dev/pts/0

MODULES_CMD=/usr/share/Modules/libexec/modulecmd.tcl

BASH_FUNC_ml%%=() {  module ml "$@"

}

BASH_FUNC_which%%=() {  ( alias;

 eval ${which_declare} ) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@

}

BASH_FUNC_module%%=() {  _module_raw "$@" 2>&1

}

BASH_FUNC_scl%%=() {  if [ "$1" = "load" -o "$1" = "unload" ]; then

 eval "module $@";

 else

 /usr/bin/scl "$@";

 fi

}

BASH_FUNC__module_raw%%=() {  eval `/usr/bin/tclsh /usr/share/Modules/libexec/modulecmd.tcl bash "$@"`;

 _mlstatus=$?;

 return $_mlstatus

}

_=/usr/bin/env

[root@RockyLinux01 ~]#

 

 

 

 

그렇지만 다시 env를 아무런 인자 없이 그냥 실행하면 원래 초기값으로 되돌려 진다는 것을 알 수 있습니다.

 

 

 

 

 

[root@RockyLinux01 ~]# env

SHELL=/bin/bash

HISTCONTROL=ignoredups

HISTSIZE=1000

HOSTNAME=RockyLinux01

GUESTFISH_OUTPUT=\e[0m

PWD=/root

LOGNAME=root

XDG_SESSION_TYPE=tty

MODULESHOME=/usr/share/Modules

MANPATH=/usr/share/man:

GUESTFISH_RESTORE=\e[0m

MOTD_SHOWN=pam

HOME=/root

LANG=ko_KR.UTF-8

LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.webp=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.m4a=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.oga=01;36:*.opus=01;36:*.spx=01;36:*.xspf=01;36:

GUESTFISH_PS1=\[\e[1;32m\]><fs>\[\e[0;31m\]

SSH_CONNECTION=192.168.19.111 52828 192.168.19.201 22

XDG_SESSION_CLASS=user

TERM=xterm

LESSOPEN=||/usr/bin/lesspipe.sh %s

USER=root

MODULES_RUN_QUARANTINE=LD_LIBRARY_PATH LD_PRELOAD

LOADEDMODULES=

SHLVL=3

GUESTFISH_INIT=\e[1;34m

XDG_SESSION_ID=2

XDG_RUNTIME_DIR=/run/user/0

SSH_CLIENT=192.168.19.111 52828 22

DEBUGINFOD_URLS=https://debuginfod.centos.org/

which_declare=declare -f

XDG_DATA_DIRS=/root/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share

PATH=/root/.local/bin:/root/bin:/usr/share/Modules/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

MODULEPATH=/etc/scl/modulefiles:/etc/scl/modulefiles:/etc/scl/modulefiles:/usr/share/Modules/modulefiles:/etc/modulefiles:/usr/share/modulefiles

DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus

MAIL=/var/spool/mail/root

SSH_TTY=/dev/pts/0

MODULES_CMD=/usr/share/Modules/libexec/modulecmd.tcl

BASH_FUNC_ml%%=() {  module ml "$@"

}

BASH_FUNC_which%%=() {  ( alias;

 eval ${which_declare} ) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@

}

BASH_FUNC_module%%=() {  _module_raw "$@" 2>&1

}

BASH_FUNC_scl%%=() {  if [ "$1" = "load" -o "$1" = "unload" ]; then

 eval "module $@";

 else

 /usr/bin/scl "$@";

 fi

}

BASH_FUNC__module_raw%%=() {  eval `/usr/bin/tclsh /usr/share/Modules/libexec/modulecmd.tcl bash "$@"`;

 _mlstatus=$?;

 return $_mlstatus

}

_=/usr/bin/env

[root@RockyLinux01 ~]#

 

 

 

 

그리고 참고로 아래 예와 같이env로 하나의 변수에 값을 할당할 수도 있지만 2개 이상의 변수에 값을 할당하여 변수리스트를 출력할 수도 있습니다.

 

 

 

 

 

[root@RockyLinux01 ~]# env HISTSIZE=2000 HOME=/tmp

SHELL=/bin/bash

HISTCONTROL=ignoredups

HISTSIZE=2000

HOSTNAME=RockyLinux01

GUESTFISH_OUTPUT=\e[0m

PWD=/root

LOGNAME=root

XDG_SESSION_TYPE=tty

MODULESHOME=/usr/share/Modules

MANPATH=/usr/share/man:

GUESTFISH_RESTORE=\e[0m

MOTD_SHOWN=pam

HOME=/tmp

LANG=ko_KR.UTF-8

LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.webp=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.m4a=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.oga=01;36:*.opus=01;36:*.spx=01;36:*.xspf=01;36:

GUESTFISH_PS1=\[\e[1;32m\]><fs>\[\e[0;31m\]

SSH_CONNECTION=192.168.19.111 52828 192.168.19.201 22

XDG_SESSION_CLASS=user

TERM=xterm

LESSOPEN=||/usr/bin/lesspipe.sh %s

USER=root

MODULES_RUN_QUARANTINE=LD_LIBRARY_PATH LD_PRELOAD

LOADEDMODULES=

SHLVL=3

GUESTFISH_INIT=\e[1;34m

XDG_SESSION_ID=2

XDG_RUNTIME_DIR=/run/user/0

SSH_CLIENT=192.168.19.111 52828 22

DEBUGINFOD_URLS=https://debuginfod.centos.org/

which_declare=declare -f

XDG_DATA_DIRS=/root/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share

PATH=/root/.local/bin:/root/bin:/usr/share/Modules/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

MODULEPATH=/etc/scl/modulefiles:/etc/scl/modulefiles:/etc/scl/modulefiles:/usr/share/Modules/modulefiles:/etc/modulefiles:/usr/share/modulefiles

DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus

MAIL=/var/spool/mail/root

SSH_TTY=/dev/pts/0

MODULES_CMD=/usr/share/Modules/libexec/modulecmd.tcl

BASH_FUNC_ml%%=() {  module ml "$@"

}

BASH_FUNC_which%%=() {  ( alias;

 eval ${which_declare} ) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@

}

BASH_FUNC_module%%=() {  _module_raw "$@" 2>&1

}

BASH_FUNC_scl%%=() {  if [ "$1" = "load" -o "$1" = "unload" ]; then

 eval "module $@";

 else

 /usr/bin/scl "$@";

 fi

}

BASH_FUNC__module_raw%%=() {  eval `/usr/bin/tclsh /usr/share/Modules/libexec/modulecmd.tcl bash "$@"`;

 _mlstatus=$?;

 return $_mlstatus

}

_=/usr/bin/env

[root@RockyLinux01 ~]#

 

 

 

 

이상과 같이 env는 변수에 값을 할당하고 변수리스트를 출력(Set each NAME to VALUE in the environment and run COMMAND.)하는 명령어라는 것을 알 수 있습니다.

 

 

 

 

 

 
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