Hi below is my code in shell scripting
for i in "${status_array[#]}"
do
if [[ $i == "*start*" ]]; then
echo "$i"
echo "${service_array[$count]} $i "
fi
count=`expr $count + 1`
isStarted=""
done
for j in "${status_array[#]}"
do
echo "$j"
done
In this script for below loop for j , $j shows few values as stop.waiting and few as start/running. but for above loop control comes to the if clause block. and also here $i shows every value as start/running, so why this happen in that case.
You should change "*start*" to *"start"*. If you place glob patterns around quotes, it would be matched in literal form.
When using [[ ]] you don't need to quote your strings as
Word splitting and pathname expansion are not performed on the words
between the [[ and ]]; tilde expansion, parameter and variable
expansion, arithmetic expansion, command substitution, process
substitution, and quote removal are performed.
And quoting disable your glob pattern.
Solution
So remove the quotes in your [[ ]] test:
if [[ $i == *start* ]]; then
echo "$i"
fi
Tests
Let's see what bash is doing with set -x
With quotes
set -x; i=starter; [[ $i == "*start*" ]] && echo "yes" || echo "no"; set +x
+ set -x
+ i=starter
+ [[ starter == \*\s\t\a\r\t\* ]]
+ echo no
no
See everything, even the * are escaped.
Without quotes
set -x; i=starter; [[ $i == *start* ]] && echo "yes" || echo "no"; set +x
+ set -x
+ i=starter
+ [[ starter == *start* ]]
+ echo yes
yes
Moar
What is the difference between test, [ and [[ ?
Related
I am novice to linux scripting. For the below example, i need to split the string as per "-" and store the output in an array as a separate element.
Later, i need to validate each element in an array if its an integer or alphanumeric. if its integer, i need to ignore that element and print only non-integer elements. The following script which i am trying is not giving expected output which should be like 'grub2-systemd-sleep-plugin'.
item = grub2-systemd-sleep-plugin-2.02-153.1
IFS='-'
read -rasplitIFS<<< "$item"
for word in "${splitIFS[#]}"; do echo $word; done
Taking a stab at this here...
Depends on how your numbers may be defined, but I believe you could use something like this to removing numbers from the output. I'm not sure if there is a more efficient way to achieve this
for word in ${splitIFS[#]}
do
c=$(echo $word | grep -c -E "^[0-9]+\.{0,}[0-9]+$")
[ $c -eq 0 ] && echo $word
done
If you're using bash, it will be faster if you use built-in tools rather than subshells.
line=grub2-systemd-sleep-plugin-2.02-153.1-foo-1
while [[ -n "$line" ]]
do if [[ "$line" =~ ^[0-9.]+- ]]
then line="${line#*-}"
elif [[ "$line" =~ ^[0-9.]+$ ]]
then break
elif [[ "$line" =~ ^([[:alnum:]]+)- ]]
then echo "${BASH_REMATCH[1]}";
line="${line#*-}"
elif [[ "$line" =~ ^([[:alnum:]]+)$ ]]
then echo "${BASH_REMATCH[1]}";
break
else echo "How did I get here?"
fi
done
or if you prefer,
shopt -s extglob
line=grub2-systemd-sleep-plugin-2.02-153.1-foo-1
while [[ -n "$line" ]]
do case "$line" in
+([0-9.])-*) line="${line#*-}" ;;
+([0-9.])) break ;;
+([[:alnum:]])-*) echo "${line%%-*}"
line="${line#*-}" ;;
+([[:alnum:]])) echo "$line"
break ;;
*) echo "How did I get here?" ;;
esac
done
I had written a help menu for reference about the usage of a shell script my_script.sh
echo $'\n\n'
echo $(printf '=%.0s' {1..100})
printf ' %.0s' {1..40}
echo "Welcome"
echo $(printf '=%.0s' {1..100})
echo $'\n'
arg=$1
echo "Input : $arg"
echo
if [[ arg -eq "-h" ]] || [[ arg -eq "-H" ]] || [[ arg -eq "-help" ]] || [[ arg -eq "-Help" ]] || [[ arg -eq "--h" ]] || [[ arg -eq "--H" ]] || [[ arg -eq "--help" ]] || [[ arg -eq "--Help" ]]; then
echo "Help menu requested...."
echo $'\n\n'
echo $(printf '~%.0s' {1..100})
printf ' %.0s' {1..43}
echo "Help Menu"
echo $(printf '~%.0s' {1..100})
echo $'\n'
exit 0
else
echo "Executing a program...."
./another_script.sh
fi
When I execute `myscript.sh -h' (or any of the '-' prefixed option), it goes to the if condition, but any other argument doesn't. What am I doing wrong here? I'm new to bash scripts.
Two simple problems with your if:
-eq is for integer comparison, = or == for strings
Use $arg in your if (instead of arg).
But: I would recommend using getopts instead of string comparison. This would make the part more robust, taking care of different ordering of parameters, or when one letter parameters are combined into a single argument.
Unfortunately I do not know the exact reason why your code does not work, but I can offer you a quick fix: You can write "==" instead of "-eq" and prefix your variable "arg" with a dollar sign. Then your script should work fine.
Working example (GNU bash 4.4.19):
arg=$1
if [[ $arg == "-h" ]] || [[ $arg == "-H" ]]; then
echo "Help!"
else
echo "Stop!"
fi
the -eq operation is only used for comparing numbers.
To compare strings uses the operation =
You forgot $ sign for variables arg in Bash, should be $arg
When we use variables in Bash, we should better use double quote.
use #() for multiple strings comparison.
so the if conditions [[ arg -eq "-h" ]] should be [[ "$arg" = "-h" ]]
When comparing a variable with multiple strings, we can use [[ "$arg" = #(-h|-H|--help|--HELP|--h|--H|-help|--HELP) ]].
if [[ "$arg" = #(-h|-H|--help|--HELP|--h|--H|-help|--HELP) ]]; then
echo "Help menu requested...."
echo $'\n\n'
echo $(printf '~%.0s' {1..100})
printf ' %.0s' {1..43}
echo "Help Menu"
echo $(printf '~%.0s' {1..100})
echo $'\n'
exit 0
else
echo "Executing a program...."
./another_script.sh
fi
In addition, we can use boxes(boxes - Command line ASCII boxes unlimited!
) to generate a comment box
cat <<EOF | boxes -a c -d shell -p a5 -s 30x9
HELP MENU
bla bla
EOF
output:
########################################
# #
# #
# HELP MENU #
# #
# bla bla #
# #
# #
########################################
I need some help in my shell script. I have this:
#!/bin/bash
for i in $*
do
if [[ $i = *[a-zA-Z] ]]
then echo $i contains just letters.
elif [[ $i = *[a-zA-Z0-9] ]]
then echo $i contains numbers and letters.
else
echo Error.
done
I would like the result to be, for example:
$ ./script.sh abCd a9d a-b
abCd contains just letters.
a9d contains numbers and letters.
Error.
But I get contains just letters in every case.
I also tried grep command too, but without success.
Your RegEx are wrong. Try the following:
#!/bin/bash
for i in $*
do
if [[ $i =~ ^[a-zA-Z]+$ ]]
then echo $i contains just letters.
elif [[ $i =~ ^[a-zA-Z0-9]+$ ]]
then echo $i contains numbers and letters.
else
echo Error.
fi
done
I tried the following but without success
[root#OBAMA~]# bash
[root#OBAMA~]# a=HelloWorld
[root#OBAMA~]# [[ $a == [A-Za-z] ]] && echo "YES ITS STRING"
( the command not prints anything )
[root#OBAMA~]# [[ $a == [A-Z][a-z] ]] && echo "YES ITS STRING"
( the command not prints anything )
Change your command lke below.
$ [[ $a =~ [A-Za-z]+ ]] && echo "YES ITS STRING"
YES ITS STRING
Use =~ operator to test an input string against a regex.
Add + next to the character class, so that it would repeat the previous pattern or token one or more times. Here it's unnecessary.
Add anchors , in-order to do an exact string match. [[ $a =~ [A-Za-z] ]] && echo "YES ITS STRING" alone will print the string YES ITS STRING because the variable a contains atleast an alphabet.
$ a="HelloWorld"
$ [[ $a =~ ^[A-Za-z]+$ ]] && echo "YES ITS STRING"
YES ITS STRING
$ a="Hello World"
$ [[ $a =~ ^[A-Za-z]+$ ]] && echo "YES ITS STRING"
$
how do you define "a string"
[[ -n $a ]] && echo variable a is not empty
[[ $a == *[[:alpha:]]* ]] && echo variable a contains a letter
shopt -s extglob failglob
[[ $a == +([[:alpha:]]) ]] && echo variable a only has letters
Your glob expressions are not matching because your checking that your variable contains only 1 character or 2 characters.
I'm unfamiliar with bash scripting. I wrote a script check arguments. the code is:
for (( i=1; i<=4; i++ ))
do
if ! [[ "$"$i =~ .*[^0-9].* ]]; then
echo "bad input was $i"
fi
done
Actually i want to split non numerical arguments, But it seems that "$"$i is wrong because the answer is always true or false independent of arguments.
can anybody tell me what is the mistake?
You seem to be trying to use indirect parameter expansion.
for (( i=1; i<=4; i++ ))
do
if ! [[ ${!i} =~ .*[^0-9].* ]]; then
echo "bad input was $i"
fi
done
However, it's cleaner to just iterate over the parameters directly, rather than over their position:
for arg in "${#:1:4}"; do
if ! [[ $arg =~ .*[^0-9].* ]]; then
echo "bad input was $arg"
fi
done
If condition should be like this:
if [[ ! "$i" =~ [^0-9] ]]; then
OR remove 2 negatives:
if [[ "$i" =~ [0-9] ]]; then
OR use glob:
if [[ "$i" == *[0-9]* ]]; then
Which means $i contains a digit 0-9
Update: Based on your comments it looks like you are looking for BASH variable indirection like this script check-num.sh:
#!/bin/bash
for (( i=1; i<=$#; i++ )); do
[[ "${!i}" != *[0-9]* ]] && echo "bad input was ${!i}"
done
You can run this script as: ./check-num.sh 1 2 x 4 a
Note how ${!i} syntax is being used here to access the variable's $1, $2, $3 etc that is called BASH variable indirection. You shouldn't use $$i for this purpose.
As per BASH manual:
If the first character of parameter is an exclamation point, a level of variable indirection is introduced. Bash uses the value of the variable formed from
the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the
value of parameter itself.
Use something like this :
for i in "$#"; do
[[ $i =~ .*[^0-9].* ]] || echo "bad input was $i"
done
N.B : It's not necessary to use doubles quotes arround the variable with the [[ internal instruction.