COUNTER=0
let COUNTER=COUNTER+1
count=`ssh -i /var/www/.ssh/id_rsa_root -o stricthostkeychecking=no $host $cmd`
count1=`echo $count | awk '{print $4}'`
printf "count1 : $count1\n"
result1=${count1/.*}
if [ "$result1" -ge "0" ]; then
echo $host
else
echo $host
exit
fi
If the value of $result1 is INTEGER and greater than zero, it'll goto IF loop (works fine for me)
But when it is not INTEGER, it is coming to else loop (which it is suppose to do) with the following error in the Output
line 55: [: : integer expression expected
but i dont want the above error in my output. I tried to use 2>/dev/null with this but no luck.
please help!
If you want to handle an empty result gracefully, check for it explicitly:
if [ -z "$result1" ]; then
: "ignoring empty string"
elif [ "$result1" -ge 0 ]; then
printf '%s\n' "$host"
else
printf '%s\n' "$host"
exit
fi
You could also check if result1 is a valid integer before making arithmetic comparisons:
function isNumber () {
[[ $1 =~ ^-?[0-9]+$ ]]
}
if ! isNumber "$result1"; then
echo "not a number"
elif [ "$result1" -ge "0" ]; then
echo "null or positive"
else
echo "negative"
fi
Change if [ "$result1" -ge "0" ]; then to
if (( result1 >= 0 )); then
This syntax won't throw any errors if result1 isn't defined (or empty) or happen to be a string somehow.
Related
Actually I am a new bash learner. I can use one condition in bash command. But how to use multiple condition in bash? I can use if statement like this:
read a
if [ $a = "y" ] ; then
echo "YES"
elif [ $a = "Y" ] ; then
echo "YES"
else
echo "NO"
fi
I am finding something like this:
read a b c
if [ $a -eq $b and $b -eq $c ] ; then
echo "EQUILATERAL"
elif [ $a -eq $b or $b -eq $c ] ; then
echo "ISOSCELES"
else
echo "SCALENE"
fi
I just want to know, what to use instead of and and or?
Use && for and (|| for or)
read a b c
if [ "$a" == "$b" ] && [ "$b" == "$c" ] ; then
echo "EQUILATERAL"
elif [ "$a" == "$b" ] || [ "$b" == "$c" ] ; then
echo "ISOSCELES"
else
echo "SCALENE"
fi
Use && and || to have multiple conditions. Additionally, change the square brackets to parentheses. Additionally change the -eq to == since you're comparing numbers and not strings. This works:
#!/bin/bash
read a b c
if (( $a == $b )) && (( $b == $c )); then
echo "EQUILATERAL"
elif (( $a == $b )) || (( $b == $c )) ; then
echo "ISOSCELES"
else
echo "SCALENE"
fi
In addition to the prior answers, the correct way to use compound expression in a single [ or test (they are the same) clause is to use -a (for and) and -o (for or).
(e.g. testing if both file1 and file2 are readable):
if [ -r "$file1" -a -r "$file2 ]
then
# do something with the files
fi
Using test itself:
if test -r "$file1" -a -r "$file2
then
# do something with the files
fi
The portable way of doing this inside test brackets is to use -a and -o. Beware however that -eq is a numeric comparison, so you need to make sure your variables are numeric before comparing them. Something like this:
#! /bin/sh
read a b c
expr "$a" : '[0-9][0-9]*$' \& "$b" : '[0-9][0-9]*$' \& "$c" : '[0-9][0-9]*$' >/dev/null || exit
if [ $a -eq $b -a $b -eq $c ] ; then
echo "EQUILATERAL"
elif [ $a -eq $b -o $b -eq $c ] ; then
echo "ISOSCELES"
else
echo "SCALENE"
fi
Here is my script, im having trouble in elif statement. I need it to exit if user enters a non negative integer as argument 1 or a string..
#!/bin/sh
n="0"
m="$1"
if test $# != "2"
then
echo "Usage: ./echon.sh <number of lines> <string>"
exit 1
elif [ $1 -eq "[^0-9]" ] || [ $1 = "[a-zA-Z]" ]
then
echo "./echon.sh: argument 1 must be a non-negative integer"
exit 1
else
while [ "$n" -lt "$m" ]
do
echo "$2"
n=$(($n + 1))
done
fi
A quick rewrite
#!/bin/bash
shopt -s extglob
if (( $# != 2 )); then
echo "Usage: $0 <number of lines> <string>"
elif [[ $1 != 0 && $1 != [1-9]*([0-9]) ]]; then
echo "$0: argument 1 must be a non-negative integer"
else
n=0
while (( n < $1 )); do
echo "$2"
((n++))
done
fi
Notes
using [[ ... ]] for string comparisons
using (( ... )) for arithmetic expressions
using extended globbing to match a non-negative integer (enforcing a non-zero number does not begin with 0, to avoid potential invalid octal numbers)
Replace your elif line with the following:
elif echo $1 | grep -qv "^[0-9][0-9]*"
When I run this bash script :
if [ [$EUID -ne 0] ]; then
echo "This script must be run as root" 1>&2
exit 1
else
printf " whathever "
exit 0
fi
I have this error :
./myScript: 15: [: Illegal number: [
Do you see any problem ?
You have syntax error in your if condition, use this if condition:
if [ "$EUID" -ne 0 ];
OR using [[ and ]]
if [[ "$EUID" -ne 0 ]];
You have syntax error in your if condition, use this if condition:
if [ "$EUID" -ne 0 ];
OR using [[ and ]]
if [[ "$EUID" -ne 0 ]];
If you use the KSH88+/Bash 3+ internal instruction [[, it's not necessary to use doubles quotes around the variables operands :
[ ~/test]$ [[ $var2 = "string with spaces" ]] && echo "OK" || echo "KO"
OK
Instead of the external command test or his fork [ :
[ ~/test]$ [ $var2 = "string with spaces" ] && echo "OK" || echo "KO"
bash: [: too many arguments
KO
[ ~/test]$ [ "$var2" = "string with spaces" ] && echo "OK" || echo "KO"
OK
Of course, you also have to choose the operators according to the type of operands :
[ ~/test]$ var1="01"
[ ~/test]$ [ "$var1" = "1" ] && echo "OK" || echo "KO"
KO
[ ~/test]$ [ "$var1" -eq "1" ] && echo "OK" || echo "KO"
OK
two suggestions apart from what everyone else has pointed out already.
rather than doing else [bunch of code because we are root] fi, just replace the else with fi. once you've tested for the failure condition you are concerned about and taken appropriate action, no need to continue to be within the body of the conditional.
$EUID is a bashism, if you would like to make this portable to shells such as ksh, replacing it with:
if [ $(id -u) -ne 0 ]; then echo "ur not root bro"; exit 1; fi
would be a good way to do it.
using
sudo bash shell_script.sh
instead of
sudo sh shell_script.sh
solved in my case.
I found an interesting Bash script that will test if a variable is numeric/integer. I like it, but I do not understand why the "0" is not recognized as a number? I can not ask the author, hi/shi is an anonymous.
#!/bin/bash
n="$1"
echo "Test numeric '$n' "
if ((n)) 2>/dev/null; then
n=$((n))
echo "Yes: $n"
else
echo "No: $n"
fi
Thank you!
UPDATE - Apr 27, 2012.
This is my final code (short version):
#!/bin/bash
ANSWER=0
DEFAULT=5
INDEX=86
read -p 'Not choosing / Wrong typing is equivalent to default (#5): ' ANSWER;
shopt -s extglob
if [[ $ANSWER == ?(-)+([0-9]) ]]
then ANSWER=$((ANSWER));
else ANSWER=$DEFAULT;
fi
if [ $ANSWER -lt 1 ] || [ $ANSWER -gt $INDEX ]
then ANSWER=$DEFAULT;
fi
It doesn't test if it is a numeric/integer. It tests if n evaluates to true or false, if 0 it is false, else (numeric or other character string) it is true.
use pattern matching to test:
if [[ $n == *[^0-9]* ]]; then echo "not numeric"; else echo numeric; fi
That won't match a negative integer though, and it will falsely match an empty string as numeric. For a more precise pattern, enable the shell's extended globbing:
shopt -s extglob
if [[ $n == ?(-)+([0-9]) ]]; then echo numeric; else echo "not numeric"; fi
And to match a fractional number
[[ $n == #(?(-)+([0-9])?(.*(0-9))|?(-)*([0-9]).+([0-9])) ]]
in bash I need to compare two float numbers, one which I define in the script and the other read as paramter, for that I do:
if [[ $aff -gt 0 ]]
then
a=b
echo "xxx "$aff
#echo $CX $CY $CZ $aff
fi
but I get the error:
[[: -309.585300: syntax error: invalid arithmetic operator (error token is ".585300")
What is wrong?
Thanks
Using bc instead of awk:
float1='0.43255'
float2='0.801222'
if [[ $(echo "if (${float1} > ${float2}) 1 else 0" | bc) -eq 1 ]]; then
echo "${float1} > ${float2}"
else
echo "${float1} <= ${float2}"
fi
use awk
#!/bin/bash
num1=0.3
num2=0.2
if [ -n "$num1" -a -n "$num2" ];then
result=$(awk -vn1="$num1" -vn2="$num2" 'BEGIN{print (n1>n2)?1:0 }')
echo $result
if [ "$result" -eq 1 ];then
echo "$num1 greater than $num2"
fi
fi
Both test (which is usually linked to as [)and the bash-builtin equivalent only support integer numbers.
Use bc to check the math
a="1.21231"
b="2.22454"
c=$(echo "$a < $b" | bc)
if [ $c = '1' ]; then
echo 'a is smaller than b'
else
echo 'a is larger than b'
fi
I would use awk for that:
e=2.718281828459045
pi=3.141592653589793
if [ "yes" = "$(echo | awk "($e <= $pi) { print \"yes\"; }")" ]; then
echo "lessthanorequal"
else
echo "larger"
fi
The simplest solution is this:
f1=0.45
f2=0.33
if [[ $f1 > $f2 ]] ; then echo "f1 is greater then f2"; fi
which (on OSX) outputs:
f1 is greater then f2
Here's another example combining floating point and integer arithmetic (you need the great little perl script calc.pl that you can download from here):
dateDiff=1.9864
nObs=3
i=1
while [[ $dateDiff > 0 ]] && [ $i -le $nObs ]
do
echo "$dateDiff > 0"
dateDiff=`calc.pl $dateDiff-0.224`
i=$((i+1))
done
Which outputs
1.9864 > 0
1.7624 > 0
1.5384 > 0