I have an issue that should not be too hard to solve, I just can't figure what I'm doing wrong.
I need to test if a command is successful or not, and the command needs to be executed from a script. The command is:
curl 127.0.0.1:5000 &> /dev/null
Right now there is no server running, so it should always fail. And it does fail when I execute it from a command line. However when I run it from inside a shell script, it fails but the exit code is 0. What could the cause of that be?
Here is the script:
if curl 127.0.0.1:5000 &> /dev/null
then
echo "sucess"
exit 0
else
echo "failure"
exit 1
fi
And here is the output:
success
curl: (7) Failed to connect to 127.0.0.1 port 5000: Connection refused
However, it does work as expected if I remove the redirection (I'm quite a beginner in shell code, but the redirection shouldn't also redirect the exit code right? So I really don't know what this means)
here is the code without redirections that works as expected (therefore that indicates a failure and has an exit code of 1):
if curl 127.0.0.1:5000
then
echo "sucess"
exit 0
else
echo "failure"
exit 1
fi
Anyone has an idea?
Edit:
I was launching the script with sh script_name.sh in zsh. When I use zsh script_name.sh it now works normally. I still don't fully understand why but at least it works!
"&> /dev/null" is interpreted differently in Bourne shell (sh), The "&" puts the command in background, you can test it with "sleep 100 &>/dev/null". Since it successfully put the command in background, it is a success, and the exit status of the backgrounded command is disregarded.
If you want it to work in Bourne shell (sh), use the traditional syntax ">/dev/null 2>&1", and it will work in newer shells as well, i.e. it is more compatible.
In a system where sh is linked to bash, it will work as is.
Related
Let's say there's this script
#!/bin/zsh
python -c 'a'
which will fail since a isn't defined. Just before the shell script exits, I want to run a command, say echo bye. How can that be achieved?
Flow is to be:
Python command above fails.
bye appears in terminal.
The zsh script exits.
I'd prefer it to affect the python command as little as possible such as indent, putting it in an if block, checking its exit code etc. In real life, the command is in fact multiple commands.
In the script you posted, the fact that the shell exits is unrelated to any error. The shell would exit, because the last argument hast been executed. Take for instance the script
#!/bin/zsh
python -c 'a'
echo This is the End
The final echo will always be exeuted, independent of the python command. To cause the script to exit, when python returns a non-zero exit code, you would write something like
#!/bin/zsh
python -c 'a' || exit $?
echo Successful
If you want to exit a script, whenever the first one of the commands produces a non-zeror exit status, AND at the same time want to print a message, you can use the TRAPZERR callback:
#!/bin/zsh
TRAPZERR() {
echo You have an unhandled non-zero exit code in your otherwise fabulous script
exit $?
}
python -c 'a'
echo Only Exit Code 0 encountered
I've got tcl script with two ways of execution bash script:
#exec bash ./run.sh
open "|bash ./run.sh r"
The bash script is shown below:
#!/bin/bash
ls
if [ "$?" != "0" ]; then
echo "ERROR: Status failed!" > status
else
echo "Everything is OK!" > status
fi
I'm using tclsh for Windows with bash from git bash. When I use:
exec bash ./run.sh
I've got in status file:
Everything is OK!
otherwise:
open "|bash ./run.sh r"
got:
ERROR: Status failed!
Is there any possibility to correctly detect exit code when opened the tcl pipe?
You don't describe whether you get different results out of the ls part of the script. That matters; the ls command is most certainly capable of changing its behaviour according to the environment in which it is invoked. This matters because Tcl executes subprocesses (on Windows) directly using the CreateProcess() system call, rather than the various wrapped versions that Cygwin and git bash use. Other possibilities are that you're launching the script in a different directory and so on.
However, in general we'd expect a script to behave very similarly when launched via exec or via open |… r as they share a common core of functionality. The only differences are to do with how output and termination are waited for.
If you create a subprocess pipeline, by default you won't get to find out about errors from it until you close the pipeline. exec generates any errors “immediately” because it doesn't return control to you until the subprocess has terminated and all output has been read.
I'd like the terminal to return to normal after the bash script has been executed.
#! /bin/bash
echo -ne "\x01\x02\x00\x00\x00\x06\x01\x05\x00\x00\x00\x00" |nc 192.168.0.119 502 > /home/pi/mb.txt
exit 0
Currently, the script runs as expected and the output goes to its destination, but the terminal then hangs after running ./script, waiting for me to hit CTRL-C. I'd like the terminal to return to normal right after the script has run.
nc -N 192.168.0.119 502
From the man page:
-N
shutdown(2) the network socket after EOF on the input. Some servers require this to finish their work.
Note that this may not be available in some versions.
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.
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