I have created a script for updating some ipaddress in iptables. Hereby I'm describing the issues which I'm facing with that.
Issues:
Comparison not happening between two variables within a script
At the end of script i need to execute a command ie; service restart/stop etc and output of the commands should be visible while executing the script.
1) Here am comparing two variable strings:
BASE=172.31.0.0
CMD=172.31.1.0
if [[ "$CMD" == "$BASE" ]]; then
echo "ip are same"
else
echo "not matched"
fi
but there is no response/output while executing the above script. Here its not comparison is not happening..Kindly suggest a best solution to resolve this issue.
2) after executing the script I need to restart the iptables:
BASE=172.31.0.0
CMD=172.31.1.0
if [[ "$CMD" == "$BASE" ]]; then
echo "ip are same"
else
echo "not matched"
fi
service iptables restart
iptables -nvL
A script should display the output of the last two lines (commands). Kindly suggest me the best solution and how to do this in a best way.
That's very odd. This should work, so if it's not working you forgot to mention something important.
How is this script being executed? Do you simply type ./script or is it executed by some service (like cron)?
Here are some of suggestions to debug:
Sanity check: see if bash works (perhaps your login shell isn't bash, so you didn't notice). Run this at the terminal:
/bin/bash -c 'echo hello world'
It prints hello world, right? How about this:
/bin/bash -c 'BASE=172.31.0.0; CMD=172.31.1.0; if [[ "$CMD" == "$BASE" ]]; then echo "ip are same"; else echo "not matched"; fi'
If any of the above doesn't work, you have a problem with your bash installation.
Instead of executing your script with ./script.sh, run it like this:
/bin/bash script.sh
Nothing? Run this:
file script.sh
If it ends with something like "with CRLF line terminators", then cdarke nailed it: the file was created on Windows with an improper tool. Recreate it on Linux or use dos2unix. But anyway, I doubt it because with a CRLF-ending file I get this printed:
bash: ./script.sh: /bin/bash^M: bad interpreter: No such file or directory
Instead of nothing at all.
Put those this line on the beginning of the file:
set -x
(below #!/bin/bash, if you have it). This ensures a debugging trace will be printed, showing each command as it is executed.
If still there is nothing shown.. put this at your script (below set -x if you put it):
touch /tmp/hi-this-is-strange
Then check if there is a /tmp/hi-this-is-strange file after you run the script.
Related
I have a simple Bash script that takes in inputs and prints a few lines out with that inputs
fortinetTest.sh
read -p "Enter SSC IP: $ip " ip && ip=${ip:-1.1.1.1}
printf "\n"
#check IP validation
if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
echo "SSC IP: $ip"
printf "\n"
else
echo "Enter a valid SSC IP address. Ex. 1.1.1.1"
exit
fi
I tried to upload them into my server, then try to run it via curl
I am not sure why the input prompt never kick in when I use cURL/wget.
Am I missing anything?
With the curl ... | bash form, bash's stdin is reading the script, so stdin is not available for the read command.
Try using a Process Substitution to invoke the remote script like a local file:
bash <( curl -s ... )
Your issue can be simply be reproduced by run the script like below
$ cat test.sh | bash
Enter a valid SSC IP address. Ex. 1.1.1.1
This is because the bash you launch with a pipe is not getting a TTY, when you do a read -p it is read from stdin which is content of the test.sh in this case. So the issue is not with curl. The issue is not reading from the tty
So the fix is to make sure you ready it from tty
read < /dev/tty -p "Enter SSC IP: $ip " ip && ip=${ip:-1.1.1.1}
printf "\n"
#check IP validation
if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
echo "SSC IP: $ip"
printf "\n"
else
echo "Enter a valid SSC IP address. Ex. 1.1.1.1"
exit
fi
Once you do that even curl will start working
vagrant#vagrant:/var/www/html$ curl -s localhost/test.sh | bash
Enter SSC IP: 2.2.2.2
SSC IP: 2.2.2.2
I personally prefer source <(curl -s localhost/test.sh) option. While it is similar to bash ..., the one significant difference is how processes handled.
bash will result in a new process being spun up, and that process will evoke commands from the script.
source on the other hand will use current process to evoke commands from the script.
In some cases that can play a key role. I admit that is not very often though.
To demonstrate do the following:
### Open Two Terminals
# In the first terminal run:
echo "sleep 5" > ./myTest.sh
bash ./myTest.sh
# Switch to the second terminal and run:
ps -efjh
## Repeat the same with _source_ command
# In the first terminal run:
source ./myTest.sh
# Switch to the second terminal and run:
ps -efjh
Results should look similar to this:
Before execution:
Running bash (main + two subprocesses):
Running source (main + one subprocess):
UPDATE:
Difference in use variable usage by bash and source:
source command will use your current environment. Meaning that upon execution all changes and variable declarations, made by the script, will be available in your prompt.
bash on the other hand will be running in as a different process; therefore, all variables will be discarded when process exits.
I think everyone will agree that there are benefits and drawbacks to each method. You just have to decide which one is better for your use case.
## Test for variables declared by the script:
echo "test_var3='Some Other Value'" > ./myTest3.sh
bash ./myTest3.sh
echo $test_var3
source ./myTest3.sh
echo $test_var3
## Test for usability of current environment variables:
test_var="Some Value" # Setting a variable
echo "echo $test_var" > myTest2.sh # Creating a test script
chmod +x ./myTest2.sh # Adding execute permission
## Executing:
. myTest2.sh
bash ./myTest2.sh
source ./myTest2.sh
./myTest2.sh
## All of the above results should print the variable.
I hope this helps.
I wonder if there are any reliable methods (cross-shell compatible) to require bash as shell interpreter for my script.
For example, I have shell script that can be run only with bash interpreter. Despite of #!/usr/bin/bash at the beginning of my script some smart user/hacker can run it directly with another shell: $ csh script.sh
This can lead to unwanted consequences.
I already thought about testing echo $0 output and exiting with error code but syntax for if statements (as long as for another conditional statements) is different among various shell interpreters. Testing directly for $BASH_VERSION variable is unreliable due to the same limitations.
Are there any cross-shell compatible and reliable way to determine current interpreter?
Thank you!
EDIT: as for now I have the following basic check for compatibility:
### error codes
E_NOTABASH=1
E_OLD_BASH=2
# perform some checks
if [ -z "$BASH_VERSION" ]
then
echo -e "ERROR: this script support only BASH interpreter! Exiting" >&2
exit $E_NOTABASH
fi
if [[ "${BASH_VERSINFO[0]}" -lt 4 ]]
then
echo -e "ERROR: this script needs BASH 4.0 or greater! Your current version is $BASH_VERSION. Exiting" >&2
exit $E_OLD_BASH
fi
Not entirely sure I understand the scope of the question.
A #! /usr/bin/env bash shebang will fail if there's no bash, but to keep it from being explicitly parsed by another shell, um...
How about -
case "$BASH_VERSION" in
4.*) : bash version 4+ so ok ;;
*) echo "please run only with bash v4+. Aborting."
exit 1 ;;
esac
If the syntax works, it is either right or hacked.
If it crashes, you're good. :)
you could check for the parent process id, command respectively
pstree -p $$ | grep -m 1 -oE '^[^\(]+'
or
ps $(ps -o ppid=$$)
I have a scenario to copy file from one server to another, for that i need to check any existing scp is in progress, have wrote a sample shell script but the condition is not being met even though syntax is correct, the main problem here is the output of ps command will gets stored in variable scpstat and the same compared for matching string in if statement, here I'm getting the output of the variable is different from executing outside of the script. can see it is formatted different in script execution when executing sh -x scpsamp.sh, why there is "sh" appended to the output, but while comparing without ps and assigning as scpstat='scp' i can able to get the condition correct, am i doing anything wrong while getting output in to the variable. please help
#!/bin/sh
scpstat=`ps -ef | grep scp | egrep -v 'grep|ssh' | awk '{print $8}')`
if [ "$scpstat" = "scp" ];
then
echo "SCP is in progress"
else
echo "No SCP in progress"
fi
sh -x output
It's notoriously difficult to extract information from the output of ps. If your system has pgrep, it's much easier:
if pgrep scp >/dev/null
then
echo "SCP is in progress"
else
echo "No SCP in progress"
fi
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
fi
The above is part of my script. When the current shell is /bin/csh my script fails with the following error:
If: Expression Syntax
Then: Command not found
If I run bash and then run my script, it runs fine(as expected).
So the question is: If there is any way that myscript can change the current shell and then interpretate rest of the code.
PS: If i keep bash in my script, it changes the current shell and rest of the code in script doesn't get executed.
The other replies are correct, however, to answer your question, this should do the trick:
[[ $(basename $SHELL) = 'bash' ]] || exec /bin/bash
The exec builtin replaces the current shell with the given command (in this case, /bin/bash).
You can use SHEBANG(#!) to overcome your issue.
In your code you are already using she-bang but make sure it is first and foremost line.
$ cat test.sh
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
else
echo "No File"
fi
$ ./test.sh
readexportfile does not exist
$ echo $SHELL
/bin/tcsh
In the above code even though I am using CSH that code executed as we mentioned shebang in the code. In case if there is no shebang then it will take the help of shell in which you are already logged in.
In you case you also check the location of bash interpreter using
$ which bash
or
$ cat /etc/shells |grep bash
I am trying to beef up my notify script. The way the script works is that I put it behind a long running shell command and then all sorts of notifications get invoked after the long running script finished.
For example:
sleep 100; my_notify
It would be nice to get the exit code of the long running script. The problem is that calling my_notify creates a new process that does not have access to the $? variable.
Compare:
~ $: ls nonexisting_file; echo "exit code: $?"; echo "PPID: $PPID"
ls: nonexisting_file: No such file or directory
exit code: 1
PPID: 6203
vs.
~ $: ls nonexisting_file; my_notify
ls: nonexisting_file: No such file or directory
exit code: 0
PPID: 6205
The my_notify script has the following in it:
#!/bin/sh
echo "exit code: $?"
echo "PPID: $PPID"
I am looking for a way to get the exit code of the previous command without changing the structure of the command too much. I am aware of the fact that if I change it to work more like time, e.g. my_notify longrunning_command... my problem would be solved, but I actually like that I can tack it at the end of a command and I fear complications of this second solution.
Can this be done or is it fundamentally incompatible with the way that shells work?
My shell is Z shell (zsh), but I would like it to work with Bash as well.
You'd really need to use a shell function in order to accomplish that. For a simple script like that it should be pretty easy to have it working in both zsh and bash. Just place the following in a file:
my_notify() {
echo "exit code: $?"
echo "PPID: $PPID"
}
Then source that file from your shell startup files. Although since that would be run from within your interactive shell, you may want to use $$ rather than $PPID.
It is incompatible. $? only exists within the current shell; if you want it available in subprocesses then you must copy it to an environment variable.
The alternative is to write a shell function that uses it in some way instead.
One method to implement this could be to use EOF tag and a master script which will create your my_notify script.
#!/bin/bash
if [ -f my_notify ] ; then
rm -rf my_notify
fi
if [ -f my_temp ] ; then
rm -rf my_temp
fi
retval=`ls non_existent_file &> /dev/null ; echo $?`
ppid=$PPID
echo "retval=$retval"
echo "ppid=$ppid"
cat >> my_notify << 'EOF'
#!/bin/bash
echo "exit code: $retval"
echo " PPID =$ppid"
EOF
sh my_notify
You can refine this script for your purpose.