I know this has been asked many times here, but I have looked through all of the previous ones and still can't resolve it. This is just a simple script that checks for a running service and takes the action I define.
#!/bin/bash
SERVICE="$1"
RESULT=`ps -a | sed -n /${SERVICE}/p`
MEM=$(ps aux | sort -rk +4 | grep $1 | grep -v grep | awk '{print $4}' | awk 'NR == 1')
if [ "${RESULT:-null}" = null ]; then
echo "$1 is NOT running"
else
echo "$MEM"
fi
if [ "$MEM" -ge 1 ]; then
mailx -s "Alert: server needs to be checked" me#admins.com
fi
This is the error I get:
./check_service: line 15: [: 5.4: integer expression expected
If I take out the command for the MEM variable and run it outside the script it returns 5.4, which is what I would expect. In my script I have tried changing the "1" to a "1.0" since the output would always be in decimal format, but that did not help. I feel like I am missing something simple here.
Error is due to the fact that bash only supports integer mathematics and your script is comparing 5.4 with 1.
You can fix your script by using:
if [[ ${MEM%.*} -ge 1 ]]l then
mailx -s "Alert: server needs to be checked" me#admins.com
fi
${MEM%.*} will strip part after decimal point and since you're just comparing it with 1 there is no need to have decimal point in variable MEM.
Related
I am trying to execute the command git diff | grep pkg/client/clientset | wc -l and check if the output is more than 0 or not. I have the following script
if [ "$(git diff | grep pkg/client/clientset | wc -l "$i")" -gt "0" ]; then
echo "Hello"
fi
I am getting the following error while executing the script. The error I am getting is
line 29: [: : integer expression expected
Any idea of what can be going wrong?
Comparing the number of output lines to zero is almost always an antipattern. diff and grep both already tell you whether there was a difference (exit code 1) or a match (exit code 0) precisely so you can say
if diff old new; then
echo "There were differences"
fi
if git diff --exit-code; then
echo "There were differences"
fi
if git diff --exit-code pkg/client/clientset; then
echo "There were differences in this specific file"
fi
if git diff | grep -q pkg/client/clientset; then
echo "Hello"
fi
Notice that git diff requires an explicit option to enable this behavior.
-- EDIT --
There were some incorrect statements in the answer, pointed-out by commentators Gordon Davisson and iBug. They have been corrected in this version of the answer. The final conclusion (remove the "$i") remains the same though.
wc -l "$i" will count the lines in the file $i. If you never used i as a variable, then i will be empty and the command will be wc -l "". The output of that will be empty on STDOUT en contain wc: invalid zero-length file name on STDERR. If the variable i is used, wc will most likely complain about a non-existing file. The point is, that wc will not read STDIN.
I also made some incorrect statements about the quoting. As pointed out, between the ( and ), it is a different quoting context. This can be shown as follows:
$ a="$(/usr/bin/echo "hop")"
$ echo $a
hop
$ b=hop
$ a="$(/usr/bin/echo "$b")"
$ echo $a
hop
Just removing "$i" from the wc-l will solve your issue.
if [ "$(git diff | grep pkg/client/clientset | wc -l)" -gt "0" ]; then
echo "Hello"
fi
Only a note, that is to long for a comment:
if [ "$(git diff | grep pkg/client/clientset | wc -l "$i")" -gt "0" ]; then
I think you will test the existence of string pkg/client/clientset to enter the then part. In this case you can use:
if git diff | grep -q pkg/client/clientset; then
grep will only returns a status because option -q. The status is true after the first occurrence of the string. At this point grep stops. And this status is used by if.
I'm trying to use this command to do different things based on the version of tmux installed.
But since the version is a float, I can't use normal bash checking, so I'm trying to use bc which takes in arguments in the form of "a
[[ echo `tmux -V | cut -d ' ' -f2` "> 1.6" | bc ]]
But if I do that, I get
-bash: conditional binary operator expected
-bash: syntax error near `-f2`>'
The first part tmux -V | cut -d ' ' -f2\ returns something like 1.6 or 1.8, so I'm trying to concatenate that with "> 1.6" to get an expression like "1.8> 1.6".
So I'm not really sure how to do this.
This is also going in a .tmux.conf file, and so I don't think I'd be able to store the result of the first part in another variable first.
You should not have an \ in the cut command. This works
echo "$(tmux -V | cut -d ' ' -f2) >1.6" | bc
Also, you may try this:
echo "$(tmux -V | awk '{print $2}') >1.6" | bc
And the test should be comparing to 1:
if [[ "$(echo "$(tmux -V | awk '{print $2}') >1.6" | bc)" -eq 1 ]]; then
echo "version above 1.6"
else
echo "please update your version"
fi
Please understand that doing a "floating point" test means that 1.11 is smaller than 1.6.
Not what is intended, I believe.
The correct test will need to split the version string on the dot and comparing both numeric (integer) values:
#!/bin/bash
IFS=' .' read _ one two <<< "$( tmux -V )"
if (( ( one == 1 && two > 6 ) || one > 1 )); then
echo "version above 1.6 present"
else
echo "please update tmux to a version higher than 1.6"
fi
I want to check if my VPN is connected to a specific country. The VPN client has a status option but sometimes it doesn't return the correct country, so I wrote a script to check if I'm for instance connected to Sweden. My script looks like this:
#!/bin/bash
country=Sweden
service=expressvpn
while true; do
if ((curl -s https://www.iplocation.net/find-ip-address | grep $country | grep -v "grep" | wc -l) > 0 )
then
echo "$service connected!!!"
else
echo "$service not connected!"
$service connect $country
fi;
sleep 5;
done
The problem is, it always says "service connected", even when it isn't. When I enter the curl command manually, wc -l returns 0 if it didn't find Sweden and 1 when it does. What's wrong with the if statement?
Thank you
Peter
(( )) enters a math context -- anything inside it is interpreted as a mathematical expression. (You want your code to be interpreted as a math expression -- otherwise, > 0 would be creating a file named 0 and storing wc -l's output in that file, not comparing the output of wc -l to 0).
Since you aren't using )) on the closing side, this is presumably exactly what's happening: You're storing the output of wc -l in a file named 0, and then using its exit status (successful, since it didn't fail) to decide to follow the truthy branch of the if statement. [Just adding more parens on the closing side won't fix this, either, since curl -s ... isn't valid math syntax].
Now, if you want to go the math approach, what you can do is run a command substitution, which replaces the command with its output; that is a math expression:
# smallest possible change that works -- but don't do this; see other sections
if (( $(curl -s https://www.iplocation.net/find-ip-address | grep $country | grep -v "grep" | wc -l) > 0 )); then
...if your curl | grep | grep | wc becomes 5, then after the command substitution this looks like:
if (( 5 > 0 )); then
...and that does what you'd expect.
That said, this is silly. You want to know if your target country is in curl's output? Just check for that directly with shell builtins alone:
if [[ $(curl -s https://www.iplocation.net/find-ip-address) = *"$country"* ]]; then
echo "Found $country in output of curl" >&2
fi
...or, if you really want to use grep, use grep -q (which suppresses output), and check its exit status (which is zero, and thus truthy, if and only if it successfully found a match):
if curl -s https://www.iplocation.net/find-ip-address | grep -q -e "$country"; then
echo "Found $country in output of curl with grep" >&2
fi
This is more efficient in part because grep -q can stop as soon as it finds a match -- it doesn't need to keep reading more content -- so if your file is 16KB long and the country name is in the first 1KB of output, then grep can stop reading from curl (and curl can stop downloading) as soon as that first match 1KB in is seen.
The result of the curl -s https://www.iplocation.net/find-ip-address | grep $country | grep -v "grep" | wc -l statement is text. You compare text and number, that is why your if statement does not work.
This might solve your problem;
if [ $(curl -s https://www.iplocation.net/find-ip-address | grep $country | grep -v "grep" | wc -l) == "0" ] then ...
That worked, thank you for your help, this is what my script looks now:
#!/bin/bash
country=Switzerland
service=expressvpn
while true; do
if curl -s https://www.iplocation.net/find-ip-address | grep -q -e "$country"; then
echo "Found $country in output of curl with grep" >&2
echo "$service not connected!!!"
$service connect Russia
else
echo "$service connected!"
fi;
sleep 5;
done
Code sample :
declare -i a=1
echo "The number of NMON instances running in Performance VM"
ps -ef | grep nmon | awk '{ print $2 }' | wc -l
echo "---------------------------------------------"
num2= ps -ef | grep nmon | awk '{ print $2 }' | wc -l
#num1=${num2%%.*}
#num2 = $(ps -ef | grep nmon | awk '{ print $2 }' | wc -l)
echo "---------------------------------------------"
echo "${num2}"
while [ "$a" -lt "$num2" ]
do
kill -USR2 $(ps -ef | grep nmon | awk '{ print $2 }' | head -1)
a=`expr $a + 1`
done
In the Output i am getting the following error
[: : integer expression expected
in the debug it shows
++ '[' 1 -lt '' ']'
that num2 is empty but when i echo the num2 value i am getting the value correctly.
Output:
The number of NMON instances running in Performance VM
1
1
thanks in advance
The 1 you see in the output is not from echo "${num2}". Like the diagnostics already tell you, this variable is empty.
The general syntax of shell scripts is
[ variable=value ...] command parameters ...
which will assign value to variable for the duration of command, then restore its original value. So the pipeline you are running temporarily sets num2 to the empty string (which apparently it already contained anyway), then runs the pipeline without storing the output anywhere (such as, I imagine you expected, in num2).
Here is a fixed version of your script, with the additional change that the Awk scripts handle stuff you used grep and head and wc for. Because the functionality of these commands is easily replaced within Awk, using external utilities is doubtful (especially so for grep which really is useless when you just run it as a preprocessor for a simple Awk script).
countnmon () {
ps -ef | awk '/[n]mon/ { ++n } END { print n }'
}
declare -i a=1
echo "The number of NMON instances running in Performance VM"
countnmon
echo "---------------------------------------------"
num2=$(countnmon)
#num1=${num2%%.*}
#num2 = $(countnmon)
echo "---------------------------------------------"
echo "${num2}"
while [ "$a" -lt "$num2" ]
do
kill -USR2 $(ps -ef | awk '/[n]mon/ { print $2; exit }')
a=`expr $a + 1`
done
The repeated code could be refactored even further to avoid all code duplication but that will somewhat hamper the readability of this simple script so I have not done that.
Whitespaces matter in bash.
The syntax for command execution is:
command arg1 arg2 ...
So,
var = value # command: var, arg1: =, arg2: value
There's are two exceptions to this rule
exporting variables to an executed command (the variables vanish after the command finishes):
var1=value1 var2=value2 .. command arg1 arg2 ...
assigning a variable (you want this one):
var=value
I have code that I use in openwrt. I need to check memory which use application
#!/bin/bash
VAR=$(ps | grep sca | grep start | awk '{print $3}')
VAG=$(cat /proc/pid/status | grep -e ^VmSize | awk '{print $2}')
if [ $VAG>28000 ]
then
echo test
fi
No matter if I use VAR or VEG(for example VAR/VAG equal 15000), I can get work this code. I always get "test"
Your if statement is incorrect. The test command (aka [) must receive separate arguments for the operands and the operator. Also, > is for string comparisons; you need to use -gt instead.
if [ "$VAG" -gt 28000 ]
Since you are using bash, you can use the more readable arithmetic command instead of [:
if (( VAG > 28000 ))