How to find out if script launched using terminal console or without, in gui by .desktop file for example?
I have look over env output and some variables looks promising to check, like test $TERM var. But I want known for sure and a compatible/portable way to do it.
This is needed for script what will have two behaviors for user input, fallback to terminal read or gui input.
The answer by #LeonidMew is incomplete and somewhat incorrect.
You should not detect GUI by presence of STDIN (that's what [ -t 0 ] test does). There are cases when none of STDIN and GUI are available, e.g. when you run the script over ssh session in non-interactive mode. This happens often for CI deploys.
Correct answer heavily depends on your task, in general there are 4 distinct environments:
App is run non-interactively, e.g. from ssh command, spawned as child process without STDIO attached, etc. GUI is missing, STDIN is missing.
App is run interactively from X-session with .desktop file or alike. GUI is present, STDIN is missing.
App is run interactively from linux terminal (ssh, bare text console, hosting recovery console, etc.). GUI is missing, STDIN is present. App can interact with user in text mode via STDIN.
App is run interactively from GUI terminal app, like xterm. GUI is present, STDIN is present.
There are 2 basic tests that can help to identify the environment:
GUI test - whether app can interact with user using graphical windows: test for $DISPLAY env variable.
STDIN test - whether app can interact with user using text console: test for file descriptor 0 (aka STDIN) with if [ -t 0 ]; ...
Combining these two test will give you the environment:
test 1 false + test 2 false: case 1 -- no user interaction available
test 1 true + test 2 false: case 2 -- interact via XWindows
test 1 false + test 2 true: case 3 -- interact via STDIN/console
test 1 true + test 2 true: case 4 -- XWindows or STDIN/console, whichever is preferred
if [ -t 0 ]; then echo "in a terminal"; fi
That tests file descriptor 0, which is stdin. If you're launching your script as a GUI, that test should be false.
Author: glenn jackman
This won't work if the script is run from a terminal, but with input
redirected. – Gordon Davisson
so for the purpose of this discussion, terminal emulator is being
conflated with linux console, and both are being distinguished from a
"gui method" which I'd thought xterm to be, as it opens in a gui... -
JosephHarriott
Purpose of this question was writing script interface usable for text or gui if script run by .desktop shortcut or other gui method.
Or:
$ [ -t 0 ] && echo "in a terminal" || echo "something else"
in a terminal
Related
I have code for setting the zsh as default shell:
if [ -t 1 ]; then
exec zsh
fi
What exactly does the command if [ -t 1 ] do here?
I have code for setting the zsh as default shell:
No, you haven't. That's not what your code does, though it produces a similar effect.
if [ -t 1 ]; then
exec zsh
fi
What exactly does the command if [ -t 1 ] do here?
The command [ -t 1 ] is executed. If it exits with status 0 (indicating success, which for the [ command means the condition evaluates to true) then the commands in the body of the if statement are executed.
It may be a bit surprising that [ is a command, rather than part of shell syntax, but that's the case. Your if could be rewritten equivalently to use the test command instead:
if test -t 1; then
# ...
The other key thing, then, is the -t 1 part. You can find out about that in the manual for the test or [ command, but to save you the trouble, it is a conditional expression that evaluates whether file descriptor 1 (the shell's standard output) is connected to a terminal. This is similar to, but not exactly the same thing as, evaluating whether the shell is an interactive one.
Overall, the code presented has the effect of replacing the current (presumably bash) shell with zsh if the standard output is connected to a terminal. This is indirect, and a bit tricky; it would probably be better to genuinely set your login shell to /bin/zsh (or wherever it is installed) via the chsh command.
if command; then other_command; fi runs command and then, if that command exits with a return code of 0 ("success"), runs other_command.
The command [...] is designed to take the place of the Boolean expressions that you find in traditional programming languages. It has a number of options for what goes between the brackets and exits with 0=success if those options evaluate to a true value.
The specific subcommand -t tests a file descriptor to see if it is attached to a terminal. The file descriptor 1 is where the script's output is going (aka "standard output" or "stdout" for short). So -t 1 is true and [ -t 1 ] returns success if and only if the output of the script is going to a terminal (instead of into a file or pipe or something).
In that case, the current shell is replaced (via exec) by a copy of zsh. Which will hopefully not run the same script, since zsh works the same way and will make the same decision and go into an infinite loop execing itself.
My requirement is like this:
I need to log in to a remote device (say Router/switch) and execute following commands.
telnet xx.xx.xx.xx
//give password here
sys
interface g x/x/x
shut
desc free-port
exit
There are Hundreds of devices for which I cannot waste time doing above damn thing 100 times. I need to write a automated script which does it. so My questions are as follows:
I use Windows system, so What is the best scripting language to be used : Ruby / shell script / perl ? (I was formerly ROR Developer, so i know Ruby, Linux terminal. Now I am working in networking domain. )
What I thought was : Put all Devices into an array and using for loop, call devices one by one and execute above said commands.
I don't have knowledge of scripting, so please guide me further. I don't know where to start from.
Step 1: decide the file structure of your program.
For example, this is the simplest structure
if_admin/
|--config.yml
|--run.rb
Step 2: write a config file or a bunch of config files that contain the different parts of the commands you need to run on the targets.
For example, you can use a yaml file like this:
xx.xx.xx.xx:
password: s3cret
router-shelf: x
slot: x
port: x
yy.yy.yy.yy:
...
Step 3: implement what you want to do
require 'yaml'
require 'net/telnet'
config = YAML.load_file('./config.yml')
config.each do |host, conf|
telnet = Net::Telnet.new('Host' => host)
telnet.login(conf['password'])
telnet.puts <<-CMD
sys
interface g #{conf['router-shelf']}/#{conf['slot']}/#{conf['port']}
shut
desc free-port
CMD
telnet.close
end
If you can use expect script , you are in luck.
#!/usr/bin/expect
set timeout 60
set cmds [list "ssh host1 ..." "ssh host2 ..." "ssh host3 ..."]
foreach cmd $cmds {
spawn -noecho bash -c $cmd
expect {
-re "password" {
exp_send "$env(PASS_WORD)\"
exp_continue
}
eof { wait } ; # at this time the last spawn'ed process has exited
}
}
Here is the rough idea of above script :-
set cmds [list.... will be used as list to store set of commands.
foreach will iterate though those commands
spawn will spawn process for each of the command. you can write multiple command with single telnet in bash, just break down commands using \ (backslash) so it is easily readable and extendable.
expect block will pass password whenever it encounter certain regex.
eof will wait till all commands in spawn process are finish.
set timeout -1 will keep loop running. i think default time for expect script is 10secs.
You can create one more foreach loop for host-list.
I think this will be enough to get you started for your automation process.
As to the question of "What is the best scripting language to be used", I would say go with one that does what you need and one that you're comfortable with using.
If you want to go with Perl, one module that you could use is Net::Telnet. Of course, you'll need Perl itself. I'd recommend using Strawberry Perl, which should already have Net::Telnet installed.
Another possible route is to use putty, which is a SSH and telnet client. You could combine that with TTY Plus, which provides an interface that uses tabs for different putty sessions. And it lets you issue commands to multiple putty sessions. This is one possibility that wouldn't involve a lot of code writing.
I am starting ftam server (ft820.rc on CentOS 5) using bash version bash 3.0 and I am having an issue with starting it from the script, namely in the script I do
ssh -nq root#$ip /etc/init.d/ft820.rc start
and the script won't continue after this line, although when I do on the machine defined by $ip
/etc/init.d/ft820.rc start
I will get the prompt back just after the service is started.
This is the code for start in ft820.rc
SPOOLPATH=/usr/spool/vertel
BINPATH=/usr/bin/osi/ft820
CONFIGFILE=${SPOOLPATH}/ffs.cfg
# Set DBUSERID to any value at all. Just need to make sure it is non-null for
# lockclr to work properly.
DBUSERID=
export DBUSERID
# if startup requested then ...
if [ "$1" = "start" ]
then
mask=`umask`
umask 0000
# startup the lock manager
${BINPATH}/lockmgr -u 16
# update attribute database
${BINPATH}/fua ${CONFIGFILE} > /dev/null
# clear concurrency locks
${BINPATH}/finit -cy ${CONFIGFILE} >/dev/null
# startup filestore
${BINPATH}/ffs ${CONFIGFILE}
if [ $? = 0 ]
then
echo Vertel FT-820 Filestore running.
else
echo Error detected while starting Vertel FT-820 Filestore.
fi
umask $mask
I repost here (on request of #Patryk) what I put in the comments on the question:
"is it the same when doing the ssh... in the commandline? ie, can you indeed connect without entering a password, using the pair of private_local_key and the corresponding public_key that you previously inserted in the destination root#$ip:~/.ssh/authorized_keys file ? – Olivier Dulac 20 hours ago "
"you say that, at the commandline (and NOT in the script) you can ssh root#.... and it works without asking for your pwd ? (ie, it can then be run from a script?) – Olivier Dulac 20 hours ago "
" try the ssh without the '-n' and even without -nq at all : ssh root#$ip /etc/init.d/ft820.rc start (you could even add ssh -v , which will show you local (1:) and remote (2:) events in a very verbose way, helping in knowing where it gets stuck exactly) – Olivier Dulac 19 hours ago "
"also : before the "ssh..." line in the script, make another line with, for example: ssh root#ip "set ; pwd ; id ; whoami" and see if that works and shows the correct information. This may help be sure the ssh part is working. The "set" part will also show you the running shell (ex: if it contains BASH= , you're running bash. Otherwise SHELL=... should give a good hint (sometimes not correct) about which shell gets invoked) – Olivier Dulac 19 hours ago "
" please try without the '-n' (= run in background and wait, instead of just run and then quit). It it doesn't work, try adding -t -t -t (3 times) to the ssh, to force it to allocate a tty. But first, please drop the '-n'. – Olivier Dulac 18 hours ago "
Apparently what worked was to add the -t option to the ssh command. (you can go up to put '-t -t -t' to further force it to try to allocate the tty, depending on the situation)
I guess it's because the invoked command expected to be run within an interactive session, and so needed a "tty" to be the stdout
A possibility (but just a wild guess) : the invoked rc script outputs information, but in a buffered environment (ie, when not launched via your terminal), the calling script couldn't see enough lines to fill the buffer and start printing anything out (like when you do a "grep something | somethings else" in a buffered environment and ctrl+c before the buffer was big enough to display anything : you end up thinking no lines were foudn by the grep, whereas there was maybe a few lines already in the buffer). There is tons to be said about buffering, and I am just beginning to read about it all. forcing ssh to allocate a tty made the called command think it was outputting to a live terminal session, and that may have turned off the buffering and allowed the result to show. Maybe in the first case, it worked too, but you could never see the output?
Question
How can one specify a user's emacs init file to load with emacsclient?
emacsclient does not understand '-u user' and '-a ALTERNATE-EDITOR' does not allow me to quote it and provide '-u user'.
For example, running:
/usr/bin/emacsclient -n -a '/usr/bin/emacs -u <username>' ~<username>/notes.txt
returns
/usr/bin/emacsclient: error executing alternate editor "/usr/bin/emacs -u <username>"
Background
I'm using emacs version 23.1.1 and emacsclient version 23.1.
emacs itself supports '-u user' to load a specified user's init file.
I use the following bash function in my aliases file to invoke emacs
# a wrapper is needed to sandwich multiple command line arguments in bash
# 2>/dev/null hides
# "emacsclient: can't find socket; have you started the server?"
emacs_wrapper () {
if [ 0 -eq $# ]
then
/usr/bin/emacsclient -n -a /usr/bin/emacs ~<username>/notes.txt 2>/dev/null &
else
/usr/bin/emacsclient -n -a /usr/bin/emacs $* 2>/dev/null &
fi
}
alias x='emacs_wrapper'
Typing x followed by a list of files:
Connects to an existing emacs server if one is running, otherwise starts a new one
Executes as a background process
Opens the list of files or my notes file if no files are provided
This works great when I'm logged in as myself. However, many production boxes require me to log in as a production user. I've separated my aliases into a bash script, therefore I can get my aliases and bash functions by simply running.
. ~<username>/alias.sh
Unfortunately, this won't let me use my .emacs file (~<username>/.emacs) :(
This problem has been driving me crazy.
If you can't include command line arguments in your alternate editor specification, then simply write a shell script which does that for you, and supply that as the alternate editor argument instead.
#!/bin/sh
emacs -u (username) "$#"
The point of the server/client model is that you have an existing Emacs with its own set of configurations, and then you connect via one or more clients.
What should the client do if the server was already configured to show the menu bar (a global setting), and the client says not to show it? What if another client attaches saying to show it?
If you want to use different settings for Emacs, use different emacs sessions.
Not having much luck Googling this question and I thought about posting it on SF, but it actually seems like a development question. If not, please feel free to migrate.
So, I have a script that runs via cron every morning at about 3 am. I also run the same scripts manually sometimes. The problem is that every time I run my script manually and it fails, it sends me an e-mail; even though I can look at the output and view the error in the console.
Is there a way for the bash script to tell that it's being run through cron (perhaps by using whoami) and only send the e-mail if so? I'd love to stop receiving emails when I'm doing my testing...
you can try "tty" to see if it's run by a terminal or not. that won't tell you that it's specifically run by cron, but you can tell if its "not a user as a prompt".
you can also get your parent-pid and follow it up the tree to look for cron, though that's a little heavy-handed.
I had a similar issue. I solved it with checking if stdout was a TTY. This is a check to see if you script runs in interactive mode:
if [ -t 1 ] ; then
echo "interacive mode";
else
#send mail
fi
I got this from: How to detect if my shell script is running through a pipe?
The -t test return true if file descriptor is open and refers to a terminal. '1' is stdout.
Here's two different options for you:
Take the emailing out of your script/program and let cron handle it. If you set the MAILTO variable in your crontab, cron will send anything printed out to that email address. eg:
MAILTO=youremail#example.com
# run five minutes after midnight, every day
5 0 * * * $HOME/bin/daily.job
Set an environment variable in your crontab that is used to determine if running under cron. eg:
THIS_IS_CRON=1
# run five minutes after midnight, every day
5 0 * * * $HOME/bin/daily.job
and in your script something like
if [ -n "$THIS_IS_CRON" ]; then echo "I'm running in cron"; else echo "I'm not running in cron"; fi
Why not have a command line argument that is -t for testing or -c for cron.
Or better yet:
-e=email#address.com
If it's not specified, don't send an email.
I know the question is old, but I just came across the same problem. This was my solution:
CRON=$(pstree -s $$ | grep -q cron && echo true || echo false)
then test with
if $CRON
then
echo "Being run by cron"
else
echo "Not being run by cron"
fi
same idea as the one that #eruciform mentioned - follows your PID up the process tree checking for cron.
Note: This solution only works specifically for cron, unlike some of the other solutions, which work anytime the script is being run non-interactively.
What works for me is to check $TERM. Under cron it's "dumb" but under a shell it's something else. Use the set command in your terminal, then in a cron-script and check it out
if [ "dumb" == "$TERM" ]
then
echo "cron"
else
echo "term"
fi
I'd like to suggest a new answer to this highly-voted question. This works only on systemd systems with loginctl (e.g. Ubuntu 14.10+, RHEL/CentOS 7+) but is able to give a much more authoritative answer than previously presented solutions.
service=$(loginctl --property=Service show-session $(</proc/self/sessionid))
if [[ ${service#*=} == 'crond' ]]; then
echo "running in cron"
fi
To summarize: when used with systemd, crond (like sshd and others) creates a new session when it starts a job for a user. This session has an ID that is unique for the entire uptime of the machine. Each session has some properties, one of which is the name of the service that started it. loginctl can tell us the value of this property, which will be "crond" if and only if the session was actually started by crond.
Advantages over using environment variables:
No need to modify cron entries to add special invocations or environment variables
No possibility of an intermediate process modifying environment variables to create a false positive or false negative
Advantages over testing for tty:
No false positives in pipelines, startup scripts, etc
Advantages over checking the process tree:
No false positives from processes that also have crond in their name
No false negatives if the script is disowned
Many of the commands used in prior posts are not available on every system (pstree, loginctl, tty). This was the only thing that worked for me on a ten years old BusyBox/OpenWrt router that I'm currently using as a blacklist DNS server. It runs a script with an auto-update feature. Running from crontab, it sends an email out.
[ -z "$TERM" ] || [ "$TERM" = "dumb" ] && echo 'Crontab' || echo 'Interactive'
In an interactive shell the $TERM-variable returns the value vt102 for me. I included the check for "dumb" since #edoceo mentioned it worked for him. I didn't use '==' since it's not completely portable.
I also liked the idea from Tal, but also see the risk of having undefined returns. I ended up with a slightly modified version, which seems to work very smooth in my opinion:
CRON="$( pstree -s $$ | grep -c cron )"
So you can check for $CRON being 1 or 0 at any time.