I am having trouble with this while loop. Here is the error I am getting currently : [: : unary operator expected (on line 3)
Here is my code:
#!/bin/bash
while [ "$option" <= 3 ]; do
echo "1) View 'HelloWorld' Text";
echo "2) View 'MyName' Text";
echo "3) View 'HappyFall' Text";
echo "4) Exit\n";
read -p "Please choose your option using numbers 1-4: " option;
if [ "$option" == 1 ]
then
cat HelloWorld
elif [ "$option" == 2 ]
then
cat MyName
elif [ "$option" == 3 ]
then
cat HappyFall
else
echo "Exiting...";
fi
done
<= is not a valid comparison in bash scripting, but -le (less than or equal) is.
There are two different types of comparison in scripting: those for strings, and those for numbers.
Stings typically use == or != for equal or not equal.
Integers, however, use:
-eq equal
-ne not equal
-lt less than
-le less than or equal
-gt greater than
-ge greater than or equal
Here's a more comprehensive list:
http://mywiki.wooledge.org/BashGuide/TestsAndConditionals#Conditional_Blocks_.28if.2C_test_and_.5B.5B.29
Error aside, this is a good use case for the select command:
options=(
"View 'HelloWorld' Text"
"View 'MyName' Text"
"View 'HappyFall' Text"
"Exit"
)
select option in "${options[#]}"; do
case $REPLY in
1) cat HelloWorld ;;
2) cat MyName ;;
3) cat HappyFall ;;
*) break ;;
esac
done
Related
I am trying to make a simple menu-driven calculator script. I am trying to make it such that after selecting A (add) or B (subtract) from the menu, it'll call the function and display the corresponding message when:
The parameters entered when function called is greater than 3
No parameters are entered when the function is called
The operator entered when the function is called is neither "+" or "-"
Right now it is doing the parameter check when I call the script ./mycalc.sh
executing the script
Am not sure how to make it check parameters after the function is called?
#!/bin/bash
display() {
echo "Calculator Menu"
echo "Please select an option between add, subtract or exit"
echo "A. Add"
echo "B. Subtract"
echo "C. Exit"
}
#initialize choice n
choice=n
if [[ $# -ne 3 ]]
then echo " You have not entered 3 parameters"
exit 1
fi
if [ $# -eq 0 ]
then
echo " You have not entered any parameters, please input 3. "
fi
if [[ $2 != [+-] ]]
then
echo " Please enter an add or subtract operator."
exit 1
fi
add() {
echo " The sum of $one + $three equals $(( $one $op $three ))"
}
subtract () {
echo " The difference of $one - $three equals $(( $one $op $three )) "
}
while [ $choice != 'C' ]
do display
read choice
if [ $choice = 'A' ]
then
read -p "Please enter two operands and the operator '+': " one op three
add $one $op $three
elif [ $choice = 'B' ]
then
read -p " Please enter two operands and the operator '-': " one op three
subtract $one $op $three
elif [ $choice = 'C' ]
then
echo "Thank you for using this program. The program will now exit."
fi
done
sleep 3
exit 0
if [ $# > 3 ]
then
echo " You need to input 3 parameters. "
fi
Within [...], the > is simply redirection. You'll find an empty file named 3 in your current directory.
Since this is an error condition for your script, you'll want to exit:
if [[ $# -ne 3 ]]; then
echo "usage: $0 operand1 operator operand2" >&2
exit 1
fi
And to test the operator, there are many ways.
case, but it's a bit verbose
case $2 in
'+'|'-') : ;;
*) echo "Operator must be + or -" >&2
exit 1
;;
esac
Within [[...]] the == and != operators are pattern matching operators
if [[ $2 != [+-] ]]; then
echo "Operator must be + or -" >&2
exit 1
fi
I commented the things I have problem.
and also, is there any other way I can exit my loop without using the exit command?.................
#!/bin/bash
while [ "$done" != "true" ] #this don't work
do
echo "Please enter one of the following options"
echo "1. Move empty files"
echo "2. Check file size"
echo "3. Which file is newer"
echo "4. File check rwx"
echo "5. Exit".
echo -n "Enter Choice: "
read scale # starting from this part for checking if user only inputs numbers 1-5 not working
if ! [[ "$scale" =~ ^[0-6]+$ ]]
then
echo "Invalid Input"
fi #up to this part is not working
read -r answer
case "$answer" in
1) ./move_empty
exit 55
;;
2) ./file_size
exit 0
;;
3) ;;
;;
4)
;;
5) done="true";;
esac
done
There are few things Which should be avoided
while [ "$done" != "true" ] --> while [ $done -ne 1 ] /* -ne is not equal to */
case "$answer" in --> case $answer in
Complete Code
var=0
flag=1
while [ $var -ne 1 ]
do
echo "Please enter one of the following options"
echo "1. Move empty files"
echo "2. Check file size"
echo "3. Which file is newer"
echo "4. File check rwx"
echo "5. Exit".
echo -n "Enter Choice: "
read scale
if [ $scale -gt 0 -a $scale -lt 6 ]
then
echo "valid Input, you can procees for switch "
else
echo "invalid input.. go again & give correct one "
flag=0
fi
if [ $flag -eq 1 ]
then
read -r answer
case $answer in
1) ./move_empty
#exit 55
break
;;
2) ./file_size
#exit 0
break
;;
3)
exit 0
;;
4)
;;
5) done="true";;
esac
fi
done
To come out from loop, without using exit command, use break. Here is the answer from man 1 bash
break [n]
Exit from within a for, while, until, or select loop.
If n is specified, break n levels. n must be ≥ 1. If n
is greater than the number of enclosing loops, all
enclosing loops are exited. The return value is 0
unless n is not greater than or equal to 1.
I want to create a select menu in it, like this:
echo "Choose your option:"
1) Factorial Calculation
2) Addition Calculator
3) Quit
And I have some shell scripts;
Factorial
./fact.sh
#!/bin/bash
fact=1
#taking input from user
echo -e "enter a number"
read n
#if enter value less than 0
if [ $n -le 0 ] ; then
echo "invalid number"
exit
fi
#factorial logic
if [ $n -gt 0 ] ; then
for((i=$n;i>=1;i--))
do
fact=`expr $fact \* $i`
done
fi
echo "The factorial of $n is $fact"
Addition
./add.sh
#!/bin/bash
#function to add two numbers
add()
{
x=$1
y=$2
echo -e "Number entered by u are: $x and $y"
echo "sum of $1 and $2 is `expr $x + $y` "
}
# main script
echo "enter first number"
read first
echo "enter second number"
read sec
#calling function
add $first $sec
echo "end of the script"
I have to create a menu, how should I proceed?
You can use select.
For your example:
select option in Factorial Addition Quit; do
case "$option" in
"Factorial")
echo "Factorial"
break ;;
"Addition")
echo "Addition"
break ;;
"Quit") exit ;;
esac
done
A shell script should take multiple condition in single line input and it should take one end of input character to perform next operation. ie.
#!/bin/bash
#Functions are defined here 1 2 3 4 5
echo "choice"
echo
echo "[1] one"
echo "[2] two"
echo "[3] three"
echo "[4] four"
echo "[5] five"
echo
read -p "Enter choice: " ch
if [ "$ch" = "1" ]; then
function_1
else
if [ "$ch" = "2" ]; then
function_2
else
if [ "$ch" = "3" ]; then
function_3
else
if [ "$ch" = "4" ]; then
function_4
else
if [ "$ch" = "5" ]; then
function_5
fi
fi
fi
fi
fi
now say end of input taking denoted by 'e' hence if I execute the .sh file and in "Enter choice"
$Enter choice: 1 3 5 e
it should execute 1 3 and 5th function one by one
how to do that?
You can iterate over all the choices until you find the 'end of input':
read -p "Enter choice: " ch
for choice in $ch; do
[ "$choice" == 'e' ] && break
eval function_$choice
done
NOTE: eval will assemble a command from the arguments and then execute it through the shell
You should iterate over your string ch until "e" appears:
#!/bin/bash
#Functions are defined here 1 2 3 4 5
echo "choice"
echo
echo "[1] one"
echo "[2] two"
echo "[3] three"
echo "[4] four"
echo "[5] five"
echo
read -p "Enter choice: " ch
for i in ${ch}
do
if [ "$i" == "1" ]; then
function_1
else if [ "$i" == "2" ]; then
function_2
else if [ "$i" == "3" ]; then
function_3
else if [ "$i" == "4" ]; then
function_4
else if [ "$i" == "5" ]; then
function_5
else if [ "$i" == "e" ]; then
break
fi
fi
fi
fi
fi
fi
but the answer of mxlian is "cleaner". i just corrent your code..
It would be better if you made each input parameter an option and used getopts ie
myProg.sh -a aArg -b bArg -c cArg
Inside myProg.sh:
while getopts "a:b:c" option
do
case $option in
a) function_1;;
b) function_2;;
c) function_3;;
*) exitFunc "Incorrect argument";; # You need to write exitFunc()
esac
done
This way you can have a missing option ie only option a and c (no b). If you do it your way and one parameter is missing (or null) say paramater 3 then parameter 4 becomes parameter 3 etc.
I keep getting unexpected End of file error while running a if else statement
#! /bin/bash
echo -e "1: Proband\n 2: mincount\n Enter an option:"
read promin
echo $promin
if ($promin == 1) then
echo -e "Enter the proband file name\n"
read proband_file
echo "$proband_file"
endif
if ($promin == 2) then
echo -e "enter the min count number\n"
read mincount
echo "$mincount mincount"
endif
I tried fi instead of elseif too. But i still get the same error. Can someone help me fix that?
This is how you write an if-statement in bash:
if - then - fi
if [ conditional expression ]
then
statement1
statement2
fi
if - then - else - fi
If [ conditional expression ]
then
statement1
statement2
else
statement3
statement4
fi
if - then - elif - else - fi
If [ conditional expression1 ]
then
statement1
statement2
elif [ conditional expression2 ]
then
statement3
statement4
else
statement5
fi
Example of a conditional expression:
#!/bin/bash
count=100
if [ $count -eq 100 ]
then
echo "Count is 100"
fi
IMPROVED
The if is syntax is not correct. In the if there should be a program (bash internal or external) run, which returns an exit code. If it is 0 then if is true, otherwise it is false. You can use grep or any other utility, like test or /usr/bin/[. But bash has a built-in test and [.
So [ "$var" -eq 1 ] returns 0 if $var equals 1, or return 1 if $var not equals 1.
In your case I would suggest to use case instead of if-then-elif-else-fi notation.
case $x in
1) something;;
2) other;;
*) echo "Error"; exit 1;;
easc
Or even use select. Example:
#!/bin/bash
PS3="Enter an option: "
select promin in "Proband" "mincount";do [ -n "$promin" ] && break; done
echo $promin
case "$promin" in
Proband) read -p "Enter the proband file name: " proband_file; echo "$proband_file";;
mincount) read -p "Enter the min count number: " mincount; echo "$mincount mincount";;
*) echo Error; exit 1;;
esac
This will print the "Enter an option: " prompt and wait until a proper answer is presented (1 or 2 or ^D - to finish the input).
1) Proband
2) mincount
Enter an option: _
Then it checks the answer in the case part. Meanwhile $promin contains the string, $REPLY contains the entered answer. It also can be used in case.
I just changed your code and I think it works now.
I think the problem is you should fi instead of endif...
#!/bin/sh
echo "1: Proband\n2: mincount\nEnter an option:"
read promin
echo $promin
if [ $promin -eq "1" ]
then
echo "Enter the proband file name\n"
read proband_file
echo "$proband_file"
elif [ $promin -eq "2" ]
then
echo "enter the min count number\n"
read mincount
echo "$mincount mincount"
fi
#! /bin/bash
echo -e "1: Proband\n2: mincount\nEnter an option:"
read promin
echo $promin
if (($promin == 1)); then
echo -e "Enter the proband file name\n"
read proband_file
echo "$proband_file"
elif (($promin == 2)); then
echo -e "Enter the min count number\n"
read mincount
echo "$mincount mincount"
fi
I don't know if you need an if-else statement or two if statemnts. The above has an if-else.
If you need two if statements, then insert a line of code below the "echo "$proband_file"" line with the text:
fi
Then replace the line "elif (($promin == 2)); then" with the following code:
if (($promin == 2)); then