Difference between ⫾ (U+2AFE) and ⫿ (U+2AFF) in the context of Dijkstra’s Guarded Command Language?

Continuing https://tex.stackexchange.com/questions/435986/how-to-draw-the-box-of-dijkstras-guarded-command-language, what is the difference in the intended usage of ⫾ (Dijkstra choice, U+2AFE) and ⫿ (n-ary Dijkstra choice, U+2AFF) in the context of the Guarded Command Language (GCL) of Dijkstra? In other words, when do you use ⫾ and when ⫿ for typesetting GCL programs? Moreover, can you confirm or reject Barbara’s answer?

Related: http://latex.org/forum/viewtopic.php?t=32939

For a command to increase something, should instructions refer to the “+” key or the “=” key?

Our software uses the =/+ and -/_ keys for opposite tasks. For example, increasing or decreasing a value, or zooming in or out. No modifier keys are used.

Here is the conundrum:

  • If we refer to it as the “plus (+) key,” users might think they have to hold Shift.
  • If we refer to it as the “equals (=) key,” we lose the intuitive dichotomy against the “minus (-) key.”

Is there:

  • Research that gives a reason to prefer one form over the other?
  • A mention of this in an authoritative style guide that establishes a convention?
  • A good example of this in the wild?

Wait Command so Unrar will finish the first .rar then move to next

Below is the command user3140225 helped me out with and it works fine:

find /home/username/source/directory/ -type f -name "*.rar" -exec unrar e -o- {} /home/username/copy/extracted/to \; -delete && rm -r /home/username/source/directory 

Except I noticed it is uraring the .rar files from the separate folders (Folder1, 2) all at one time.

My structure is

  • SourceDirectory


    File .rar


    File .rar

I would like the one unrar to finish first before it goes on to the next one.

I am using cronjobs to run these commands. So if there is another way I would be grateful.

command not found: sudo

After reading about the lately discovered vulnerability with sudo, I decided to update to 1.8.28 manually. I downloaded deb file from sudo.ws and used dpkg to install it, and it failed due to lack of dependencies.

sudo dpkg -i debs/sudo_1.8.28-1_ubu1804_i386.deb  (Reading database ... 232031 files and directories currently installed.) Preparing to unpack .../sudo_1.8.28-1_ubu1804_i386.deb ... Unpacking sudo:i386 (1.8.28-1) over (1.8.27-1ubuntu1.1) ... dpkg: dependency problems prevent configuration of sudo:i386: sudo:i386 depends on libc6. sudo:i386 depends on libpam0g. sudo:i386 depends on libpam-modules. sudo:i386 depends on zlib1g. sudo:i386 depends on libselinux1. sudo:i386 depends on libaudit1.  dpkg: error processing package sudo:i386 (--install): dependency problems - leaving unconfigured Processing triggers for man-db (2.8.5-2) ... Errors were encountered while processing: sudo:i386 

After that I can’t call sudo any more and it seems to be damaged cause I can locate it in /usr/bin/sudo:

l /usr/bin/sudo -rwsr-xr-x 1 root root 479K Oct 10 20:15 /usr/bin/sudo 

Since there is no Root user available on Ubuntu I was wondering if there is any solution other than rebooting as root in recovery mode?

Mails sent from the command line not appearing in inbox or spam folder

I sent some test mails using the command line. In the log I can see that status = sent, but I am not getting any emails in my inbox or spam folder.

Oct 11 15:51:01 ip-10-0-1-80 postfix/local[20606]: 724AB6D5B: to=<root@localhost>, orig_to=<root>, relay=local, delay=0.01, delays=0.01/0/0/0, dsn=2.0.0, status=sent (delivered to mailbox) 

Error: Expected a right parenthesis in expression at (1) after `make` command

I am compiling a software following this tutorial (called PRESTO), but when I type ./configure, I receive the following message:

$   make && sudo make install Making all in src make[1]: enter directory "/home/user/Softwares/tempo/src" /usr/bin/f77  -g -O2 -c -o bnryddfwhiecc.o bnryddfwhiecc.f bnryddfwhiecc.f:130:71: Error: Expected a right parenthesis in expression at (1) Makefile:468: set of instructions for the objective "bnryddfwhiecc.o" failed  make[1]: *** [bnryddfwhiecc.o] Error 1 make[1]: exit directory "/home/user/Softwares/tempo/src" Makefile:359: set of instructions for the objective "all-recursive" failed make: *** [all-recursive] Errore 1 

I believe it has to do with the excessive length of the lines in the code. I have tried to add a & character to the sixth column of the “following” line, or right after the end of the long line, basically what is said here, but did not work.

I would rather use a command to disable the long-lines errors, instead of going to modify each line of each file. But I do not know enough to take actions.

customizing command prompt error

when I try to customize the command prompt by following maru’s comment.

Via the terminal:https://askubuntu.com/a/789921/1003835

so I change my command prompt setting.

the path through Edit → Preferences → Profiles

edit the current profile, to change the command: enter image description here

after this, I can’t open the command prompt. How can I do to fix this error?

Terminal command for getting information about the time and user of all the commands executed in all sessions of terminal

I want to know which user executed which command on terminal and when i.e. if any of the user does “rmdir abc” and removes a specific directory , i should know which command he executed and at what time.And i don’t want it for a single session, this data should be available to me like we maintain logs, so that i can analyze it for any point of time.

I tried the history command as well and also added time to it but it does not show “Users” of the command and also it is session based ,so it’s data does not get appended to ~/.bash_history file unless the session is exited. Also ~/.bash_history does not show time and user so it’s not usefull.Can anyone help me please.I just want to see which user executed which command from the moment the system is started and at what time.