I'm quite new to bash scripting and i've been working on a small bash file that can do a few things for me. First of all, i'm calling this from a C function using system() and i'd like the script to return a value (1 for error, 0 for OK). Is this possible?
int kinit() {
int err = system("/home/bluemoon/Desktop/GSSExample/kinitScript.sh");
}
Second, using Zenity, i managed to create a pop up window to insert user/password. Now, according to what the user does, multiple things should happen. If he closes the window or clicks "cancel", nothing should happen. If he clicks "OK", then i should check the input (for empty text boxes or something).
Assuming a correct input, i will use Expect to run a kinit program (it's a promt related with Kerberos) and log in. Now, if the password is correct, the prompt closes and the script should return 0. If it's not, the prompt will show something like "Kinit: user not found". I wanted to, in any case of error (closing window, clicking cancel or wrong credentials) return 1 in my script and return 0 on success.
#!/bin/bash
noText=""
ENTRY=`zenity --password --username`
case $? in
0)
USER=`echo $ENTRY | cut -d'|' -f1`
PW=`echo $ENTRY | cut -d'|' -f2`
if [ "$USER"!="$noText" -a "$PW"!="$noText" ]
then
/usr/bin/expect -c 'spawn kinit '`echo $USER`'; expect "Password for '`echo $USER`':" { send "'`echo $PW`'\r" }; interact'
fi
;;
1)
echo "Stop login.";;
-1)
echo "An unexpected error has occurred.";;
esac
My if isn't working properly, the expect command is always run. Cancelling or closing the Zenity window also always lead to case "0". I've also tried to return a variable but it says i can only return vars from inside functions?
Well, if anyone could give me some pointers, i'd appreciate it.
Dave
i'd like the script to return a value
Sure, just use exit in appropriate places
exit: exit [n]
Exit the shell.
Exits the shell with a status of N. If N is omitted, the exit status
is that of the last command executed.
My if isn't working properly, the expect command is always run.
if [ "$USER" != "$noText" -a "$PW" != "$noText" ]
# ^ ^ ^ ^
# | | | |
# \----- notice spaces ----/
Related
I have an existing function is_active_instance, which determines if a database instance is running (true) or not. I am working in a new function called is_inactive_instance which needs to return true if is_active_instance returns false.
How can I call is_active_instance from is_inactive_instance and negate its return to return True to main program?
I already tried to call is_instance_active with ! to change the result of the original function.
is_active_instance(){
dbservice=""
if is_mysql_db
then
dbservice="mysqld"
elif is_mariadb_db
then
dbservice="mysqld"
elif is_postgre_db
then
dbservice='postgresql'
fi
[ $(ps -ef | grep -v grep | grep $dbservice* | wc -l) > 0 ]
}
is_inactive_instance(){
[ [ ! is_active_instance ] ]
}
if is_active_instance
then
echo "Is active instance"
elif is_inactive_instance
then
echo "Is inactive instance"
else
echo "Other result"
fi
In Main body I will need to be able to detect if the instance is running, stopped or other for my purposes.
Don't use any [s:
is_inactive_instance(){
! is_active_instance
}
Also see Comparing numbers in Bash for how to make your is_active_instance work.
Here is an example of how to do this in BASH. Your code is on the right track but needs syntax changes to work in BASH.
Instead of checking for a NOT you would check for "Yes" or "No", and you may change the outputs to zeroes and ones if you wish and test for those.
Copy the code between CODE STARTS and CODE ENDS into ./active_instance.sh.
Type the line below and press RETURN.
chmod 755 ./active_instance.sh
CODE STARTS HERE ==================
#!/usr/bin/env bash
for some_db in mariadb mysqld postgres oracle sybase
do
echo -n "Checking ${some_db}..."
set `ps -ef|grep -v grep|grep ${some_db}|wc`
if test ${1} -gt 0
then
echo "Yes"
else
echo "No"
fi
done
CODE ENDS HERE ==================
To run, type the line below and press RETURN.
./active_instance.sh
Sample execution:
./active_instance.sh
Checking mariadb...Yes
Checking mysqld...Yes
Checking postgres...Yes
Checking oracle...No
Checking sybase...No
After struggling with this issue for several hours and searching here and failing to come up with a matching solution, it's time to ask:
In bash (4.3) I'm attempting to do a combination of the following:
Create an array
For loop through the values of the array with a command that isn't super fast (curl to a web server to get a value), so we background each loop to parallelize everything to speed it up.
Set the names of the values in the array to variables assigned to values redirected to it from a command via "read"
Background each loop and get their PID into a regular array, and associate each PID with the related array value in an associative array so I have key=value pairs of array value name to PID
Use "wait" to wait for each PID to exit 0 or throw an error telling us which value name(s) in the array failed to exit with 0 by referencing the associative array
I need to be able export all of the VAR names in the original array and their now-associated values (from the curl command results) because I'm sourcing this script from another bash script that will use the resulting exported VARs/values.
The reason I'm using "read" instead of just "export" with "export var=$(command)" or similar, is because when I background and get the PID to use "wait" with in the next for loop, I actually (incorrectly) get the PID of the "export" command which always exits 0, so I don't detect an error. When I use read with the redirect to set the value of the VAR (from name in the array) and background, it actually gets the PID of the command and I catch any errors in the next loop with the "wait" command.
So, basically, this mostly appears to work, except I realized the "read" command doesn't actually appear to be substituting the variable to the array name value properly in a way that the redirected command sends its output to that name in order to set the substituted VAR name to a value. Or, maybe the command is just entirely wrong so I'm not correctly redirecting the result of my command to a VAR name I'm attempting to set.
For what it's worth, when I run the curl | python command by hand (to pull the value and then parse the JSON output) it is definitely succeeding, so I know that's working, I just can't get the redirect to send the resulting output to the VAR name.
Here's a example of what I'm trying to do:
In parent script:
# Source the child script that has the functions I need
source functions.sh
# Create the array
VALUES=(
VALUE_A
VALUE_B
VALUE_C
)
# Call the function sourced from the script above, which will use the above defined array
function_getvalues
In child (sourced) script:
function_getvalues()
{
curl_pids=( )
declare -A value_pids
for value in "${VALUES[#]}"; do
read ${value} < <(curl -f -s -X GET http://path/to/json/value | python3 -c "import sys, json; print(json.load(sys.stdin)['data']['value'])") & curl_pids+=( $! ) value_pids+=([$!]=${value})
done
for pid in "${curl_pids[#]}"; do
wait "$pid" && echo "Successfully retrieved value ${value_pids[$pid]} from Webserver." || { echo "Something went wrong retrieving value ${value_pids[$pid]}, so we couldn't get the output data needed from Webserver. Exiting." ; exit 1 ; }
done
}
The problem is that read, when run in the background, isn't connected to a standard in.[details] Consider this simplified, working example with comment how to cripple it:
VALUES=( VALUE_A VALUE_B )
for value in "${VALUES[#]}"; do
read ${value} < <(echo ${RANDOM}) # add "&" and it stops working
done
echo "VALUE_A=${VALUE_A}"
echo "VALUE_B=${VALUE_B}"
You might be able to do this with coproc, or using read -u with automatic file descriptor allocation, but really this is a job for temporary files:
tmpdir=$(mktemp -d)
VALUES=( VALUE_A VALUE_B )
for value in "${VALUES[#]}"; do
(sleep 1; echo ${RANDOM} > "${tmpdir}"/"${value}") &
done
for value in "${VALUES[#]}"; do
wait_file "${tmpdir}"/"${value}" && {
read -r ${value} < "${tmpdir}"/"${value}";
}
done
echo "VALUE_A=${VALUE_A}"
echo "VALUE_B=${VALUE_B}"
rm -r "${tmpdir}"
This example uses wait_file helper, but you might use inotifywait if you don't mind some dependencies on OS.
I have a C program that I want to run without having to manually type commands into. I have 4 commands (5 if you count the one to exit the program) that I want given to the program and I don't know where to start. I have seen some stuff like
./a.out <<<'name'
to pass in a single string but that doesn't quite work for me.
Other issues I have that make this more difficult are that one of the commands will give an output and that output needs to be a part of a later command. If I had access to the source code I could just brute force in some loops and counters so I am trying to get a hold of it but for now I am stuck working without it. I was thinking there was a way to do this with bash scripts but I don't know what that would be.
In simple cases, bash script is a possibility: run the executable in coproc (requires version 4). A short example:
#!/bin/bash
coproc ./parrot
echo aaa >&${COPROC[1]}
read result <&${COPROC[0]}
echo $result
echo exit >&${COPROC[1]}
with parrot (a test executable):
#!/bin/bash
while [ true ]; do
read var
if [ "$var" = "exit" ]; then exit 0; fi
echo $var
done
For a more serious scenarios, use expect.
Is there a way to trap/catch a invalid password when you use sudo? Basically I want to return a specific exit code if the sudo password is invalid. I don't want to avoid sudo or get around it, I just want to close/exit a script in a matter of my choosing.
Based on the man page of sudo(8), there is no easy way for evaluating the exact error reasons for a failure:
Exit Value
Upon successful execution of a program, the exit status from sudo will
simply be the exit status of the program that was executed.
Otherwise, sudo exits with a value of 1 if there is a
configuration/permission problem or if sudo cannot execute the given
command. In the latter case the error string is printed to the
standard error. If sudo cannot stat(2) one or more entries in the
user's PATH, an error is printed on stderr. (If the directory does not
exist or if it is not really a directory, the entry is ignored and no
error is printed.) This should not happen under normal circumstances.
The most common reason for stat(2) to return ''permission denied'' is
if you are running an automounter and one of the directories in your
PATH is on a machine that is currently unreachable.
The only "ugly" approach, which comes to my mind is to parse the result of stderr to determine the error reason:
#!/bin/bash
tmpfile=`mktemp`
sudo echo "dummy" 2>$tmpfile
if [ $? == 1 ]; then
if [ `cat $tmpfile | grep -x "sudo.*incorrect password attempts" | wc -l` == 1 ]; then
# exit due to failed password attempts
echo "too many failed password attempts"
else
# other reason, for instance configuration
echo "other reason"
fi
fi
rm $tmpfile
Note, however, that this approach is not upgrade-safe and moreover language-dependent: If a patch to sudo changes the text which is shown to the user in case of a wrong password, or the user logs on in a different language, this coding will not be able to handle this properly.
Pretty simple, I need to test a C program by inputting a large number of integers into it. To do this, for this particularly case, I need to run the program, then when it waits for user input (scanf("%d, integer)), I need to give it the integer from the loop I'm currently at.
right now I have
for i in {1..5};
do
(echo -n "$i" && ./a2 $i)
done
but it still just waits for user input, then after user input is given, prints the integer of the loop I'm on. I've tried a few examples from similar problems I've found on stack exchange and elsewhere but so far no luck. I haven't ever really needed to mess about with shell scripting before so it's probably something simple I'm doing backasswordsly but no one else has done wrong before.
Try this!
for i in `seq 1 1000`; do echo $i | ./a2; done
Your solution
echo -n "$i" && ./a2 $i
would pass $i as argument for a2 not input.
I think what you need is not usually done using shell script.
You can write a c code to generate your input, which in this case is numbers from 1-10000. Let that file be testGenerator.c. Then, run this on your terminal:
gcc testGenerator.c
./a.out >input
This will create a file, named input which will have numbers from 1 to 10000, which is of course the o/p of testGenerator.c.
Then, if your program, in which you want input is compiled into a2, as I can see, you can run it as:
./a2 <input >output
and you will get the required output in the file output. If you don't write >output here, you will see o/p on terminal.
Also, when you are running this script, you are actually running the a2 10000 times and giving a number as command line argument, which is very different from taking input from stdin which of course, scanf does.
for i in {1..1000}; do echo $i | ./a2; done