After exiting custom startup shell script, exit into default startup shell? - shell

You have to excuse me if I use the wrong language here of if I'm asking an obvious but that is, after all, why I'm here.
I'm just getting to grips with shell scripting and have written a small script that is "Run as a custom command instead of my shell" to make things a little easier for the things I might want to do. Here's what I've got.
#
# Custom console startup script.
#
path_to_scripts=~/Scripts
echo "Hello $USERNAME, what would you like to do?"
echo "Options:"
echo "-l Continue in local machine"
echo "-s Connect to server"
read response
case $response in
"l") echo "Contunie within local machine.";;
"s") $path_to_scripts/connect_to_server;;
*) echo "Invalid command. Exiting.";;
esac
So my terminal starts up with this script and if I select 's' it runs the 'connect_to_server' script fine and connects then I'm in!
However when I enter an invalid command, or key in 'l' to exit and continue as normal the console says 'The child process exited normally with status 0.'
I know that it has just quit and the script has exited but what I want to do is just run the default shell so that I am then in my local machine at ~, as if id just started up console with default settings. What do I need to run in order to do this?

Run exec "$SHELL" to replace the current process with your normal shell.

Related

Logging into server (ssh) with bash script

I want to log into server based on user's choice so I wrote bash script. I am totally newbie - it is my first bash script:
#!/bin/bash
echo -e "Where to log?\n 1. Server A\n 2. Server B"
read to_log
if [ $to_log -eq 1 ] ; then
echo `ssh user#ip -p 33`
fi
After executing this script I am able to put a password but after nothing happens.
If someone could help me solve this problem, I would be grateful.
Thank you.
The problem with this script is the contents of the if statement. Replace:
echo `ssh user#ip -p 33`
with
ssh user#ip
and you should be good. Here is why:
Firstly, the use of back ticks is called "command substitution". Back ticks have been deprecated in favor of $().
Command substitution tells the shell to create a sub-shell, execute the enclosed command, and capture the output for assignment/use elsewhere in the script. For example:
name=$(whoami)
will run the command whoami, and assign the output to the variable name.
the enclosed command has to run to completion before the assignment can take place, and during that time the shell is capturing the output, so nothing will display on the screen.
In your script, the echo command will not display anything until the ssh command has completed (i.e. the sub-shell has exited), which never happens because the user does not know what is happening.
You have no need to capture the output of the ssh command, so there is no need to use command substitution. Just run the command as you would any other command in the script.

script file : command stopped

I made simple script. file name is sutest.
#!/bin/bash
cd ~/Downloads/redis-4.0.1/src
./redis-server
echo "uid is ${UID}"
echo "user is ${USER}"
echo "username is ${USERNAME}"
I runed script.$ . sutest
But, script code is stopped at ./redis-server.
So I can't see echo messages.
I want to make this kind of script files. How can I do that??
I would be appreciate your help.
Let's say more general case.
myscript1 file executes process like redis-server above.
another myscript2 file executes process like redis-server above.
another myscript3 file executes process like redis-server above.
How can I run three script files simultaneously??
I want to do job in ssh connection.
To make the matter worse, If I can't use screen or tmux??
Add a '&' char at the end of the row
./redis-server &
this char permits to run in backgroud the job, and the script continues.
Just do the echos first:
cd ~/Downloads/redis-4.0.1/src
echo "uid is ${UID}"
echo "user is ${USER}"
echo "username is ${USERNAME}"
exec ./redis-server
The use of exec is a small trick (which you can omit if you prefer): it replaces the shell script with redis-server, so the shell script is no longer running at all. Without exec, you end up with the shell script waiting around for redis-server to finish, which is unnecessary if the script will do nothing further.
If you don't like that for some reason, you can keep the original order:
cd ~/Downloads/redis-4.0.1/src
./redis-server & # run in background
echo "uid is ${UID}"
echo "user is ${USER}"
echo "username is ${USERNAME}"
wait # optional

Exiting a shell script with an error

basically I have written a shell script for a homework assignment that works fine however I am having issues with exiting. Essentially the script reads numbers from the user until it reads a negative number and then does some output. I have the script set to exit and output an error code when it receives anything but a number and that's where the issue is.
The code is as follows:
if test $number -eq $number >dev/null 2>&1
then
"do stuff"
else
echo "There was an error"
exit
The problem is that we have to turn in our programs as text files using script and whenever I try to script my program and test the error cases it exits out of script as well. Is there a better way to do this?
The script is being run with the following command in the terminal
script "insert name of program here"
Thanks
If the program you're testing is invoked as a subprocess, then any exit command will only exit the command itself. The fact that you're seeing contrary behavior means you must be invoking it differently.
When invoking your script from the parent testing program, use:
# this runs "yourscript" as its own, external process.
./yourscript
...to invoke it as a subprocess, not
# this is POSIX-compliant syntax to run the commands in "yourscript" in the current shell.
. yourscript
...or...
# this is bash-extended syntax to run the commands in "yourscript" in the current shell.
source yourscript
...as either of the latter will run all the commands -- including exit -- inside your current shell, modifying its state or, in the case of exit, exec or similar, telling it to cease execution.

How-to check if Linux shell script is executed by a cronjob?

Is it possible to identify, if a Linux shell script is executed by a user or a cronjob?
If yes, how can i identify/check, if the shell script is executed by a cronjob?
I want to implement a feature in my script, that returns some other messages as if it is executed by a user. Like this for example:
if [[ "$type" == "cron" ]]; then
echo "This was executed by a cronjob. It's an automated task.";
else
USERNAME="$(whoami)"
echo "This was executed by a user. Hi ${USERNAME}, how are you?";
fi
One option is to test whether the script is attached to a tty.
#!/bin/sh
if [ -t 0 ]; then
echo "I'm on a TTY, this is interactive."
else
logger "My output may get emailed, or may not. Let's log things instead."
fi
Note that jobs fired by at(1) are also run without a tty, though not specifically by cron.
Note also that this is POSIX, not Linux- (or bash-) specific.

exit not working as expected in Bash

I use SSH Secure Shell client to connect to a server and run my scripts.
I want to stop a script on some conditions, so when I use exit, not only the script stops, but all the client disconnects from the server!, Here is the code:
if [[ `echo $#` -eq 0 ]]; then
echo "Missing argument- must to get a friend list";
exit
fi
for user in $*; do
if [[ !(-f `echo ${user}.user`) ]]; then
echo "The user name ${user} doesn't exist.";
exit
fi
done
A picture of the client:
Why is this happening?
You use source to run the script, this runs it in the current shell. That means that exit terminates the current shell and with that the ssh session.
replace source with bash and it should work, or better put
#!/bin/bash
on to of the file and make it executable.
exit returns from the current shell - If you've started a script by running it directly, this will exit the shell that the script is running in.
return returns from a function or sourced file (TY Dennis Williamson) - Same thing, but it doesn't terminate your current shell.
break returns from a loop - Similar to return, but can be used anywhere within a loop to stop processing more items. This is probably what you want.
if you are running from the current shell, exit will obviously exit from the shell and disconnect you. try running it in a new shell ( use a . before the script) or else use 'return' instead of exit

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