Can anybody tell me what's wrong in this script, it's not working. When I run it, there is no output/error on the screen.
The script is to monitor a log file to check the value of one of the columns, and if it is more than 20 it will echo a message.
#!/bin/bash
while true ; do
COUNT=`tail -f /monitoring/log.20160121|cut -d" " -f39`
echo $COUNT
if [ $COUNT -gt 20 ] ;then
echo "Count is high"
break
fi
sleep 10
done
tail -f does not exit, so your script gets stuck there. I assume you are just interested in the last line of the log; tail -n 1 does that.
Other points:
Indentation: not sure how much got lost while copy pasting, but proper indentation massively increases readability of your code
Variable names: all uppercase variable names are discouraged as they might clash with reserved (environment) variable names
Command substitution with backticks (` `) is discouraged and the form $( ) is preferred; makes for example nesting easier
Since you're using Bash, you can use the (( )) conditional construct, which is better suited for comparing numbers than [ ]
Together:
#!/bin/bash
while true; do
count=$(tail -n 1 /monitoring/log.20160121 | cut -d " " -f 39)
echo $count
if (( count > 20 )); then
echo "Count is high"
break
fi
sleep 10
done
Related
I have a following list.txt file with the content
cat list.txt
one
two
zero
three
four
I have a shell script (check.sh) like below,
for i in $(cat list.txt)
do
if [ $i != zero ]; then
echo "the number is $i"
else
exit 1
fi
done
it gives output like below,
./check.sh
the number is one
the number is two
I want to have script which continue with the rest of the items in the list.txt, but it should not process zero and continue with the rest of item.
eg.
the number is one
the number is two
the number is three
the number is four
I tried using "return" but it did not work, gave error.
./check.sh: line 6: return: can only `return' from a function or sourced script
About exit (and return)
The command exit will quit running script. There is no way to continue.
As well, return command will quit function. There in no more way to continue.
About reading input file
For processing line based input file, you'd better to use while read instead of for i in $(cat...:
Simply try:
while read -r i;do
if [ "$i" != "zero" ] ;then
echo number $i
fi
done <list.txt
Alternatively, you could drop unwanted entries before loop:
while read -r i;do
echo number $i
done < <( grep -v ^zero$ <list.txt)
Note: In this specific case, ^zero$ don't need to be quoted. Consider quoting if your string do contain special characters or spaces.
If you have more than one entries to drop, you could use
while read -r i;do echo number $i ;done < <(grep -v '^\(zero\|null\)$' <list.txt)
Alternatively, once input file filtered, use xargs:
If your process is only one single command, you could avoid bash loop by using xargs:
xargs -n 1 echo number < <(grep -v '^\(zero\|null\)$' <list.txt)
How to use continue in bash script
Maybe you are thinking about something like:
while read -r i;do
if [ "$i" = "zero" ] ;then
continue
fi
echo number $i
done <list.txt
Argument of continue is a number representing number of loop to shortcut.
Try this:
for i in {1..5};do
for l in {a..d};do
if [ "$i" -eq 3 ] && [ "$l" = "b" ] ;then
continue 2
fi
echo $i.$l
done
done
(This print 3.a and stop 3 serie at 3.b, breaking 2 loop level)
Then compare with
for i in {1..5};do
for l in {a..d};do
if [ "$i" -eq 3 ] && [ "$l" = "b" ] ;then
continue 1
fi
echo $i.$l
done
done
(This print 3.a , 3.c and 3.d. Only 3.b are skipped, breaking only 1 loop level)
I have been working on a Bash script to beep when the PC is too hot.
I have removed the beep to try identifying the problem.
What I have so far:
temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
echo $temp
if ["$temp" -gt "30.1"]
then
echo "temp hot"
else
echo "temp ok"
fi
My output is
54.1
temp.sh: line 4: [54.1: command not found
temp ok
Removing the if statement just outputs
54.1
so I think it's the if statement that's not working.
You should use double parenthesis (( )) to do arithmetic expressions, and since Bash cannot handle decimal values, you just have to remove the dot (as if you want to multiply it by ten).
temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
max_temp=50.2
(( ${temp//./} > ${max_temp//./} )) && echo "temp hot" || echo "temp ok"
Be sure to use the same format for both values (especially leading zeros, 54.10 would become 5410).
If the format cannot be guaranteed, there is a second method, as mentioned by Benjamin W, using bc. You can send to this command a logical operation involving floats, it returns 0 if true, 1 otherwise.
temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
max_temp=50.2
(( $(echo "$temp > $max_temp" | bc) )) && echo "temp hot" || echo "temp ok"
Your immediate problem is syntax error -- you omitted the space between the command ([ -- /bin/[) and its arguments ($temp). The last argument of [ must be ] -- your script is missing a blank there too, which makes the last argument "30.1"]. The quotes aren't necessary here, BTW, and only make things harder to read.
This is a generic sh-scripting quation, it has nothing to do with FreeBSD nor with temperature-measuring.
my script check if the arguments are files or folders
if it is a file, he count the number of lines
after that, if the number of lines is great then 20 or less he do some instructions
the problem is in this instructionn= cat $a | wc -l
My script:
#!/usr/bin/env bash
echo 'Hello this is the test of' `date`
echo 'arguments number is ' $#
if [ $# -eq 4 ]
then
for a in $#
do
if [ -d $a ]
then
ls $a > /tmp/contenu
echo "contenu modified"
elif [ -f $a ]
then
# this instruction must set a numeric value into n
echo "my bad instruction"
n= cat $a | wc -l
echo "number of lines = " $n
# using the numeric value in a test (n must be numeric and takes the number of lines in the current file)
if [ $n -eq 0 ]
then
echo "empty file"
elif [ $n -gt 20 ]
then
echo ` head -n 10 $a `
else
cat $a
fi
else
echo "no file or directory found"
fi
done
else
echo "args number must be 4"
fi
This is the output of the execution of the incorrect instruction
my bad instruction
5
number of lines =
ExamenEx2.sh: line 19: [: -eq : opérateur unaire attendu
The line n= cat $a | wc -l is an offending instruction. Always remember that bash shell scripting is extremely case-sensitive. Your command is interpreted by the shell as having to run two separate commands
n= cat $a | wc -l
#^^ ^^^^^^^^^^^^^^
#1 2
The first part just stores an empty string to the variable n and the next prints the line count of the file stored in variable a. Notice that the shell does not throw errors for this. Because it is not violating the syntax (just the semantics are wrong). But the line count is never assigned to the variable n.
The error is seen when the conditional if [ $n -eq 0 ] is hit when you are doing a comparison with an empty variable on the LHS.
You wanted to run a command and store its output, you need command-substitution($(..)) for that. Assuming the $a contains a name of a file just do
n=$(wc -l < "$a")
Note, that I've removed the useless cat usage and piping it to wc. But wc can read from an input stream directly.
Also note that you have multiple bad practices in your script. Remember to do the following
Always double-quote the shell variables - "$#", "$#", [ -f "$a" ], [ -d "$a" ]
Don't use the `` for command-substitution, because it is not easily nestable and you might have issues related to quoting also.
You can use conditional expression [[ if you are sure if the script is running under bash in which a variable containing spaces can be used without quoting on the LHS
I am trying to write this code so that if the process reads map finished in the pipe it increments a variable by 1 so that it eventually breaks out of the while loop. Otherwise it will add unique parameters to a keys file. However it goes into an infinite loop and never breaks out of the loop.
while [ $a -le 5 ]; do
read input < map_pipe;
if [ $input = "map finished" ]; then
((a++))
echo $a
else
sort -u map_pipe >> keys.txt;
fi
done
I decided to fix it for you, not sure if this is what you wanted, but I think I am close:
#!/bin/bash
a=0 #Initialize your variable to something
while [ $a -le 5 ]; do
read input < map_pipe;
if [ "$input" = "map finished" ]; then #Put double quotes around variables to allow values with spaces
a=$(($a + 1)) #Your syntax was off, use spaces and do something with the output
else
echo $input >> keys.txt #Don't re-read the pipe, it's empty by now and sort will wait for the next input
sort -u keys.txt > tmpfile #Instead sort your file, don't save directly into the same file it will break
mv tmpfile keys.txt
#sort -u keys.txt | sponge keys.txt #Will also work instead of the other sort and mv, but sponge is not installed on most machines
fi
done
This is just a simple problem but I don't understand why I got an error here. This is just a for loop inside an if statement.
This is my code:
#!/bin/bash
if (!( -f $argv[1])) then
echo "Argv must be text file";
else if ($#argv != 1) then
echo "Max argument is 1";
else if (-f $argv[1]) then
for i in `cut -d ',' -f2 $argv[1]`
do
ping -c 3 $i;
echo "finish pinging host $i"
done
fi
Error is in line 16, which is the line after fi, that is a blank line .....
Can someone please explain why i have this error ????
many, many errors.
If I try to stay close to your example code:
#!/bin/sh
if [ ! -f "${1}" ]
then
echo "Argv must be text file";
else if [ "${#}" -ne 1 ]
then
echo "Max argument is 1";
else if [ -f "${1}" ]
then
for i in $(cat "${1}" | cut -d',' -f2 )
do
ping -c 3 "${i}";
echo "finish pinging host ${i}"
done
fi
fi
fi
another way, exiting each time the condition is not met :
#!/bin/sh
[ "${#}" -ne 1 ] && { echo "There should be 1 (and only 1) argument" ; exit 1 ; }
[ ! -f "${1}" ] && { echo "Argv must be a file." ; exit 1 ; }
[ -f "${1}" ] && {
for i in $(cat "${1}" | cut -d',' -f2 )
do
ping -c 3 "${i}";
echo "finish pinging host ${i}"
done
}
#!/usr/local/bin/bash -x
if [ ! -f "${1}" ]
then
echo "Argument must be a text file."
else
while-loop-script "${1}"
fi
I have broken this up, because I personally consider it extremely bad form to nest one function inside another; or truthfully to even have more than one function in the same file. I don't care about file size, either; I've got several scripts which are 300-500 bytes long. I'm learning FORTH; fractalism in that sense is a virtue.
# while-loop-script
while read line
do
IFS="#"
ping -c 3 "${line}"
IFS=" "
done < "${1}"
Don't use cat in order to feed individual file lines to a script; it will always fail, and bash will try and execute the output as a literal command. I thought that sed printing would work, and it often does, but for some reason it very often substitutes spaces for newlines, which is extremely annoying as well.
The only absolutely bulletproof method of feeding a line to a script that I know of, which will preserve all space and formatting, is to use while-read loops, rather than substituted for cat or for sed loops, as mentioned.
Something else which you will need to do, in order to be sure about preserving whitespace, is to set the internal field seperator (IFS) to something that you know your file will not contain, and then resetting it back to whitespace at the end of the loop.
For every opening if, you must have a corresponding closing fi. This is also true for else if. Better use elif instead
if test ! -f "$1"; then
echo "Argv must be text file";
elif test $# != 1; then
echo "Max argument is 1";
elif test -f "$1"; then
for i in `cut -d ',' -f2 "$1"`
do
ping -c 3 $i;
echo "finish pinging host $i"
done
fi
There's also no argv variable. If you want to access the command line arguments, you must use $1, $2, ...
Next point is $#argv, this evaluates to $# (number of command line args) and argv. This looks a lot like perl.
Furthermore, testing is done with either test ... or [ ... ], not ( ... )
And finally, you should enclose at least your command line arguments in double quotes "$1". If you don't and there is no command line argument, you have for example
test ! -f
instead of
test ! -f ""
This lets the test fail and go on to the second if, instead of echoing the proper message.