linux command

screen – Linux Command คำสั่งสร้าง session screen ขึ้นมาใหม่อีกจอ

screen

Linux Command – screen ใช้ในการสร้าง session screen ขึ้นมาใหม่อีกจอ

 

คำสั่ง

1. สร้าง screen session

$ screen
or
$ screen -S name

 

2. แยก session ออกจาก session screen ปัจจุบัน (detach)

Ctl+a d
$ screen -d SCREENID

 

3. แสดง session screen เปิดอยู่

$ screen -ls

 

4. กลับสู่ session screen เดิม (reattach)

$ screen -r
$ screen -r <SCREENID>
$ screen -r name

 

5. ปิด session screen

Ctl+a k

 

6. เปิด session screen โดยเก็บ log

$ screen -L

 

7. Lock session screen

Ctl+a x

 

โครงสร้างคำสั่ง

 screen [ -options ] [ cmd [ args ] ]
 screen -r [[pid.]tty[.host]]
 screen -r sessionowner/[[pid.]tty[.host]]

 

รายละเอียด

เป็นคำสั่งที่ใช้ในการสร้าง session screen ขึ้นมาใหม่อีกจอ ทำให้เราสามารถทำงานได้มากกว่า 1 หน้าจอ โดยคำสั่ง screen จะทำการแยก session ออกมาจาก terminal และยังสามารถเชื่อมต่อกลับไปได้ใหม่ และต่อให้แยกออกมาแล้ว process ก็ยังทำงานปกติต่อไปภายใต้การจัดการของ screen

 

Option

 -a include all capabilities (with some minor exceptions) in each window's termcap, even if screen must redraw parts of the display in order to implement a function.

 -A Adapt the sizes of all windows to the size of the current terminal. By default, screen tries to restore its old window sizes when attaching to resizable terminals (those with
 "WS" in its description, e.g. suncmd or some xterm).

 -c file
 override the default configuration file from "$HOME/.screenrc" to file.

 -d|-D [pid.tty.host]
 does not start screen, but detaches the elsewhere running screen session. It has the same effect as typing "C-a d" from screen's controlling terminal. -D is the equivalent to
 the power detach key. If no session can be detached, this option is ignored. In combination with the -r/-R option more powerful effects can be achieved:

 -d -r Reattach a session and if necessary detach it first.

 -d -R Reattach a session and if necessary detach or even create it first.

 -d -RR Reattach a session and if necessary detach or create it. Use the first session if more than one session is available.

 -D -r Reattach a session. If necessary detach and logout remotely first.

 -D -R Attach here and now. In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first. If it was not running create it and
 notify the user. This is the author's favorite.

 -D -RR Attach here and now. Whatever that means, just do it.

 Note: It is always a good idea to check the status of your sessions by means of "screen -list".

 -e xy
 specifies the command character to be x and the character generating a literal command character to y (when typed after the command character). The default is "C-a" and `a',
 which can be specified as "-e^Aa". When creating a screen session, this option sets the default command character. In a multiuser session all users added will start off with
 this command character. But when attaching to an already running session, this option changes only the command character of the attaching user. This option is equivalent to
 either the commands "defescape" or "escape" respectively.

 -f, -fn, and -fa
 turns flow-control on, off, or "automatic switching mode". This can also be defined through the "defflow" .screenrc command.

 -h num
 Specifies the history scrollback buffer to be num lines high.

 -i will cause the interrupt key (usually C-c) to interrupt the display immediately when flow-control is on. See the "defflow" .screenrc command for details. The use of this
 option is discouraged.

 -l and -ln
 turns login mode on or off (for /var/run/utmp updating). This can also be defined through the "deflogin" .screenrc command.

 -ls [match]
 -list [match]
 does not start screen, but prints a list of pid.tty.host strings and creation timestamps identifying your screen sessions. Sessions marked `detached' can be resumed with
 "screen -r". Those marked `attached' are running and have a controlling terminal. If the session runs in multiuser mode, it is marked `multi'. Sessions marked as `unreachable'
 either live on a different host or are `dead'. An unreachable session is considered dead, when its name matches either the name of the local host, or the specified parameter,
 if any. See the -r flag for a description how to construct matches. Sessions marked as `dead' should be thoroughly checked and removed. Ask your system administrator if you
 are not sure. Remove sessions with the -wipe option.

 -L tells screen to turn on automatic output logging for the windows.

 -m causes screen to ignore the $STY environment variable. With "screen -m" creation of a new session is enforced, regardless whether screen is called from within another screen
 session or not. This flag has a special meaning in connection with the `-d' option:

 -d -m Start screen in "detached" mode. This creates a new session but doesn't attach to it. This is useful for system startup scripts.

 -D -m This also starts screen in "detached" mode, but doesn't fork a new process. The command exits if the session terminates.

 -O selects a more optimal output mode for your terminal rather than true VT100 emulation (only affects auto-margin terminals without `LP'). This can also be set in your
 .screenrc by specifying `OP' in a "termcap" command.

 -p number_or_name|-|=|+
 Preselect a window. This is useful when you want to reattach to a specific window or you want to send a command via the "-X" option to a specific window. As with screen's
 select command, "-" selects the blank window. As a special case for reattach, "=" brings up the windowlist on the blank window, while a "+" will create a new window. The com‐
 mand will not be executed if the specified window could not be found.

 -q Suppress printing of error messages. In combination with "-ls" the exit value is as follows: 9 indicates a directory without sessions. 10 indicates a directory with running
 but not attachable sessions. 11 (or more) indicates 1 (or more) usable sessions. In combination with "-r" the exit value is as follows: 10 indicates that there is no session
 to resume. 12 (or more) indicates that there are 2 (or more) sessions to resume and you should specify which one to choose. In all other cases "-q" has no effect.

 -Q Some commands now can be queried from a remote session using this flag, e.g. "screen -Q windows". The commands will send the response to the stdout of the querying process. If
 there was an error in the command, then the querying process will exit with a non-zero status.

 The commands that can be queried now are:
 echo
 info
 lastmsg
 number
 select
 time
 title
 windows

 -r [pid.tty.host]
 -r sessionowner/[pid.tty.host]
 resumes a detached screen session. No other options (except combinations with -d/-D) may be specified, though an optional prefix of [pid.]tty.host may be needed to distin‐
 guish between multiple detached screen sessions. The second form is used to connect to another user's screen session which runs in multiuser mode. This indicates that screen
 should look for sessions in another user's directory. This requires setuid-root.

 -R resumes screen only when it's unambiguous which one to attach, usually when only one screen is detached. Otherwise lists available sessions. -RR attempts to resume the
 youngest (in terms of creation time) detached screen session it finds. If successful, all other command-line options are ignored. If no detached session exists, starts a new
 session using the specified options, just as if -R had not been specified. The option is set by default if screen is run as a login-shell (actually screen uses "-xRR" in that
 case). For combinations with the -d/-D option see there. Note: Time-based session selection is a Debian addition.

 -s program
 sets the default shell to the program specified, instead of the value in the environment variable $SHELL (or "/bin/sh" if not defined). This can also be defined through the
 "shell" .screenrc command. See also there.

 -S sessionname
 When creating a new session, this option can be used to specify a meaningful name for the session. This name identifies the session for "screen -list" and "screen -r" actions.
 It substitutes the default [tty.host] suffix.

 -t name
 sets the title (a.k.a.) for the default shell or specified program. See also the "shelltitle" .screenrc command.

 -T term
 Set the $TERM environment varible using the spcified term as opposed to the defualt setting of screen.

 -U Run screen in UTF-8 mode. This option tells screen that your terminal sends and understands UTF-8 encoded characters. It also sets the default encoding for new windows to
 `utf8'.

 -v Print version number.

 -wipe [match]
 does the same as "screen -ls", but removes destroyed sessions instead of marking them as `dead'. An unreachable session is considered dead, when its name matches either the
 name of the local host, or the explicitly given parameter, if any. See the -r flag for a description how to construct matches.

 -x Attach to a not detached screen session. (Multi display mode). Screen refuses to attach from within itself. But when cascading multiple screens, loops are not detected; take
 care.

 -X Send the specified command to a running screen session. You may use the -S option to specify the screen session if you have several screen sessions running. You can use the -d
 or -r option to tell screen to look only for attached or detached screen sessions. Note that this command doesn't work if the session is password protected.

 -4 Resolve hostnames only to IPv4 addresses.

 -6 Resolve hostnames only to IPv6 addresses.

 

กลุ่มคำสั่ง

termcap(5), utmp(5), vi(1), captoinfo(1), tic(1)

 

Reference:

คำสั่ง Unix – Linux Command

Linux, Unix

 

Author: Suphakit Annoppornchai

Credit: https://saixiii.com

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