Too many arguments with && operator in shell? - shell

if [ $(ps -ef | grep date) ] && [ $(ps -ef | grep time) ]
then
echo "success"
else
exit 1
fi
is giving [: too many arguments error
What is going wrong?
From a comment:
There are two processes running and I want to check if these two processes are running if executing my automated tool. For that I need to check if those two processes are running, you are right when you say grep is included in arguments it always succeeds I want to check only if two processes are running leaving out grep part. Can I do some thing like checking $? == 0 but how would I do that for both processes?

The [ command expects rather limited list of values. The output of your ps -ef commands could be generating a lot of data, which won't look like [ value1 = value2 ] etc which is what [ expects.
You could try:
if [ "$(ps -ef | grep date)" ] && [ "$(ps -ef | grep time)" ]
then echo "success"
else exit 1
fi
This will report success if there is at least one command referencing date and at least one command referencing time (and since the grep commands includes that argument, it should always succeed), but that may not be what you're after. With a single argument, as enforced by the double quotes, the [ command checks whether the argument is an empty string or not (success if it is not).
What are you really trying to do?

Better do this, it will be lighter than multiple subshells $( ) and pipes | (many fork()s in the background) :
if pidof &>/dev/null date && pidof &>/dev/null time; then
echo "success"
else
exit 1
fi
No need the test commands :
[ # POSIX test
or
[[ # bash enhanced test
or
test # word test
we use boolean logic here.

Related

Bash script for searching a specific word in terminal output

I'm trying to implement a bash script who supposed to search for a word in a Python script terminal output.
The Python script doesn't stop so "&" in the end of the command is needed but the "if [ $? == 0 ] ; then" condition doesn't work.
How it can be solved?
Thanks, Gal.
#!/bin/bash
#Check if Pixhawk is connected
PORT=/dev/ttyPixhawk
end=$((SECONDS+3))
not_exists=f
/usr/local/bin/mavproxy.py --daemon --non-interactive --master=$PORT | grep 'Failed' &> /dev/null &
while [ $SECONDS -lt $end ] ; do
if [ $? == 0 ] ; then
not_exists=t
fi
sleep 1
done
if [ $not_exists=t ] ; then
echo "Not Exists"
else
echo "Exists"
fi
kill $(pgrep -f '/usr/local/bin/mavproxy.py')
Bash doesn't know anything about the output of background commands. Check for yourself with [ 5444 -lt 3 ] & echo $?.
your if statement wouldn't work in any case because $? checks for the return value of the most recent previous command, which in this case is your while loop.
You have a few different options. If you're waiting for some output, and you know how long it is in the output until whatever target you're looking for occurs, you can have the python write to a file and keep checking on the file size with a timeout for failure.
You can also continue with a simple timed approach as you have where you just check the output after a few seconds and decide success or failure based on that.
You can make your python script actually end, or provide more error messages, or write only the relevant parts to file that way.
Furthermore, you really should run your script through shellcheck.net to notice more problems.
You'll need to define your goal and use case more clearly to get real help; all we can really say is "your approach will not work, but there are definitely approaches which will work"
You are checking the status of grep command output inside while loop using $?. This can be done if $? is the next command to be fired after grep and if grep is not a back-group process . But in your script, $? will return the status of while [$SECONDS -lt $end ]. You can try to re-direct the output to a temp file and check it's status
/usr/local/bin/mavproxy.py --daemon --non-interactive --master=$PORT | grep 'Failed' &> tmp.txt &
sleep 3
# If file exists and it's size is greater than 0, [ -s File] will return true
if [ -s tmp.txt ]; then
echo 'pattern exists'
else
echo 'pattern not exists'
fi

ps command in sh script not include the top command

I have written a script to check process is running or not,it work fine but while testing it, i have found that it not include top command count running in other terminal
check-process.sh
#!/bin/sh
OK=1
CRITICAL=0
PROCESS_NUM=$( ps -ef | grep $1 | grep -v "grep "|grep -v "sh"|wc -l )
#echo $PROCESS_NUM
if [ $PROCESS_NUM = $OK ]
then
echo "OK"
elif [ $PROCESS_NUM = $CRITICAL ]
then
echo "CRITICAL"
elif [ $PROCESS_NUM > $OK ]
then
echo "MULTIPLE process are runing"
else
echo "error"
fi
And i run top command in two terminals and run this script as follow:
./check-process.sh top
and out put is 0 CRITICAL , but when i run normal command ps -ef |grep -v "grep "| wc -l it gives two counts.
That mess of greps just has to go.
One "trick" for finding processes by name without finding your grep is to use a regular expression. That is, after all, what the Global Regular Expression Print command is for. You can use parameter expansion to construct a safe regular expression based on your input string, perhaps like this:
#!/bin/sh
if [ -z "$1" ]; then
echo "I'd love me an option." >&2
exit 1
fi
OK=1
CRITICAL=0
x="${1#?}" # make a temporary string missing the 1st chararcter,
re="[${1%$x}]$x" # then place the 1st character within square brackets.
PROC_COUNT=$( ps -ef | grep -w -c "$re" ) # yay, just one pipe.
if [ "$PROC_COUNT" -eq "$OK" ]; then
echo "OK"
elif [ "$PROC_COUNT" -eq "$CRITICAL" ]; then
echo "CRITICAL"
elif [ "$PROC_COUNT" -gt "$OK" ]; then
echo "MULTIPLE process are running"
else
echo "error"
fi
There are a few notable changes here:
I added something to fail with better explanation if no option is given.
The pipeline, of course. And the lines that create $re.
We're using -gt and -eq to test numeric values. man test for details.
I renamed your count variable to be clearer. What is a "PROCESS_NUM" really? Sounds like a PID to me.
All variables are quoted. I don't need to tell you why, you have the Google.
That said, you should also consider using pgrep instead of any sort of counting pipe, if it's available on your system. Try running pgrep and see what your OS tells you.

Grep issues with if statement in shell script

I'm having an issue with tail & grep in shell script if statement. If I run tail -5 mylog.log | grep -c "Transferred: 0" in shell, it runs as it should, but in this shell script if statement:
# Parse log for results
if [ tail -1 "$LOGFILE" | grep -c "Failed" ] ; then
RESULT=$(tail -1 "$LOGFILE")
elif [ tail -5 "$LOGFILE" | grep -c "Transferred: 0" ] ; then
RESULT=""
else
RESULT=$(tail -5 "$LOGFILE")
fi
I get
... [: missing `]'
grep: ]: No such file or directory
for both of the grep lines.
It's clearly to do with the closing ] being seen as part of the grep (and thus missing) but I'm using the correct whitespace so I can't figure out what's going on? What am I doing wrong here?
Thanks,
PJ
Immediate Issue / Immediate Fix
Take out the brackets.
if tail -1 "$logfile" | grep -q "Failed" ; then
[ is not part of if syntax. Rather, it's a synonym for the command named test (which is typically both available as a shell builtin and an external binary, like /bin/test or /usr/bin/test).
Thus, your original code was running [ tail -1 "$logfile", and piping its result to grep -q "Failed" ]. The first [ was failing because it didn't see an ending ] -- which is mandatory when invoked by that name rather than with the name test -- and also because its parameters weren't a test it knew how to parse; and the second grep didn't know what the ] it was being piped meant, trying to find a file by that name.
Other Notes
Try to run external commands -- like tail -- as little as possible. There's a very significant startup cost.
Consider the following, which runs tail only once:
#!/bin/bash
# ^^^^- IMPORTANT: bash, not /bin/sh
last_5_lines="$(tail -5 "$logfile")"
last_line="${last_5_lines##*$'\n'}"
if [[ $last_line = *Failed* ]]; then
result=$last_line
elif [[ $last_5_lines =~ 'Transferred:'[[:space:]]+'0' ]]; then
result=''
else
result=$last_5_lines
fi

Read unix log for message and then perform action

I am looking to create a shell script to read the message log and when finds the correct string perform an action. So far I have the following:
#!/bin/bash
string="ntp engine ready"
tail -n 0 -f /var/log/messages | \
while read LINE
do
echo "$LINE | grep -q $string"
if [ $? == 0];then
shttpclient "http://127.0.0.1/do/action"
fi
done
But, I get the following error:
grep: engine: No such file or directory
grep: ready: No such file or directory
Even when I see the logger has outputted ntp engine ready.
Firstly, you need to fix your quotes:
echo "$LINE" | grep -q "$string"
Secondly, you can simply do:
if echo "$LINE" | grep -q "$string"; then
rather than checking the return code $? manually. Remember that [ is a command too and if is just checking its return code.
If you do need to use [, remember that ] is an argument to the command so it is essential to surround it with spaces:
if [ $? = 0 ]
I have also removed the second = as it is a bash extension to support it. Actually you are doing an integer comparison, so really it should be one of the following:
if [ $? -eq 0 ] # POSIX compliant
if (( $? == 0 )) # bash arithmetic context
Alter the line as follows:
echo "$LINE" | grep -q "$string"
The quotes were not set correctly. Like when you execute that: grep -q ntp engine ready; ntp is the string to search and engine and ready are the files. It must look like: grep -q "ntp engine ready".

why does pgrep fail in this process monitor?

I have a monitor shell script that does effectively monitor and keep a process running. But it often fails in the sense that it starts a second, third or more instance of the process. I have also seen the pgrep command (pgrep -n -f wx_nanoserver) return the wrong pid at the command line...
Here's my script:
#!/bin/bash
check_process() {
# echo "$ts: checking $1"
[ "$1" = "" ] && return 0
[ `pgrep -n -f $1` ] && return 1 || return 0
}
while [ 1 ]; do
# timestamp
ts=`date +%T`
NOW=`date +"%Y%m%d-%H%M%S"`
# echo "$ts: begin checking..."
check_process "wx_nanoserver"
[ $? -eq 0 ] && echo "$ts: not running, restarting..." && `php /var/www/wx_nanoserver.php > /var/www/logs/wx_output_$NOW.log 2> /var/www/logs/wx_error_$NOW.log &`
sleep 5
done
try:
pgrep -n -f "$1" && return 1 || return 0
if you use [ ], you will try to check pgrep stdout data, and your script did not compare it with empty space or sth, without [ ], will using pgrep exit code.
Two weird things about your script:
[ `pgrep -n -f $1` ] && return 1 || return 0
works through side effects. The ``` part evaluates to either the pid of the process if found, or nothing if no process is found. The single[notation is a synonym for thetestbuiltin (or command on earlier systems) which happens to returntrueif its argument is a nonempty string andfalseif it is given no argument. So when a pid is found, the test becomes something like[ 1234 ]which evaluates to true and[ ]` otherwise, which evaluates to false. That is indeed what you want, but it would be cleaner to write:
pgrep -n -f "$1" &>/dev/null && return 1 || return 0
Another thing is
`php /var/www/wx_nanoserver.php > /var/www/logs/wx_output_$NOW.log 2> /var/www/logs/wx_error_$NOW.log &`
where you use command substitution for no apparent reason. You're asking bash to evaluate the output of your command rather than simply running it. As its output is redirected, it always evaluates to an empty string so it has no further effect. A side effect is that the command is run in a subshell, which is a good thing to deamonize it. Though, it would be cleaner to write:
( php /var/www/wx_nanoserver.php > /var/www/logs/wx_output_$NOW.log 2> /var/www/logs/wx_error_$NOW.log & )
Not sure though what the actual problem might be. Seems to be working that way anyhow.
Final note, the back tick `` notation has been deprecated in favour of the$()` notation.

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