I have the following bash script:
#!/bin/bash
if [ ! -f numbers ]; then echo 0 > numbers; fi
count = 0
while [[$count != 100]]; do
count = `expr $count + 1`
done
When I run it in terminal on my Mac, I get the following output:
seq_file_gen.sh: line 3: count: command not found
seq_file_gen.sh: line 4: [[: command not found
Why am I getting these errors? This script was given to me by my teacher so I have no idea why I can't get this script to run. Any help would be greatly appreciated.
EDIT:
This is the correct way to write this script (with spaces)
#!/bin/bash
if [ ! -f numbers ]; then echo 0 > numbers; fi
count=0
while [[ $count != 100 ]]; do
count=`expr $count + 1`
done
Add spaces before/after [[ and ]] like so:
while [[ $count != 100 ]]; do
Related
I'm trying to make a bash script that reads integers from a file (one number per line, name of the file is passed as the script argument), finds maximum, minimum and sum. I've got a problem with the part, where I'm comparing variables, though. Code below (I've skipped here the part which checks whether the file exists or is empty):
#!/bin/bash
min=`cat "$1" | head -n 1`
max=$min
sum=0
lw=`cat "$1" | wc -l`
while [ $lw -gt 0 ];
do
num=`cat "$1" | tail -n $lw | head -n 1`
if [ "$num" -gt "$max" ]
then
max=$num
elif [ "$num" -lt "$min" ]
then
min=$num
fi
sum=$[sum+num]
lw=$[$lw-1]
done
echo "Maximum: $max"
echo "Minimum: $min"
echo "Sum: $sum"
With this code I'm getting errors in lines 13 and 16: [: : integer expression expected
If I change the comparision part inside the while loop to:
if [ $num -gt $max ]
then
max=$num
elif [ $num -lt $min ]
then
min=$num
fi
I'm getting errors:
line 13: [: -gt: unary operator expected
line 16: [: -lt: unary operator expected
What am I doing wrong? I'm a total newbie in bash, so I'll be extremely grateful for any help.
Data that I used for testing:
5
6
8
2
3
5
9
10
Probably your input file contains DOS line endings or other improper formatting. Your code should work for well-formed inputs.
However, the proper way to loop over the lines in a file is
#!/bin/bash
min=$(sed 1q "$1")
max=$min
sum=0
while read -r num; do
if [ "$num" -gt "$max" ]
then
max=$num
elif [ "$num" -lt "$min" ]
then
min=$num
fi
((sum+=num))
done<"$1"
echo "Maximum: $max"
echo "Minimum: $min"
echo "Sum: $sum"
Notice also that backticks and $[[...]]] use syntax which has been obselescent for decades already.
My guess would be that the expression
num=`cat "$1" | tail -n $lw | head -n 1`
assigns to num some value that is not a number in one of the iterations. I would suggest adding echo "$num" in the prev line to check this assumption
Another thing: instead of reading lines using cat | tail | head it is easier to read file line by line using the following syntax
while IFS= read -r line
do
echo "$line"
done < "$input"
This will read contents of input file into line variable.
See here for explanations about IFS= and -r https://www.cyberciti.biz/faq/unix-howto-read-line-by-line-from-file/ - both of them not really necessary in your case
I'm looking for a rather simple solution to prompt integer numbers (one each line) into a terminal and in return for entering the equity-sign get all of them summed up.
I guess it has to look like this:
#!/bin/bash
read X
read Y
echo " $ (( X + Y ) ) "
somehow I fail to amend it properly.
Please see if below script helps. If you have any questions, please let us know.
#!/bin/bash
sum=0
number='^[0-9]+$'
equal='='
while :
do
read input
if ! [[ $input =~ $number ]] && ! [[ $input =~ $equal ]] ; then
echo -e "Please provide only numbers!"
elif [[ $input =~ $equal ]] ; then
echo -e "Sum : $sum"
break
else
let sum+=$input
fi
done
Sample Output
10
201
2202
2323
=
Sum : 4736
I'm using bash and this is my code
for i in $(seq 20)
do
if [ $i % 3 == 0 ]
then
echo HI
else
echo $i
fi
done
So the output should be:
1
2
hi
4
5
hi
...
and so on.
But I keep getting this error when I run my shell.
script.sh 4: [: 1: unexpected operator
1
then it just goes on like that until 20.
I've tried different things but i can't get it to work.
Even a bit simpler:
if ((i%3 == 0)) # No '$' needed
then
....
You need to change the line containing the if to:
if [[ $((i%3)) == 0 ]]
That will work.
Use this
for i in {1..20}
do
if [ `expr $i % 3` == 0 ]
then
echo HI
else
echo $i
fi
done
It should be like below mentioned format,
if [ $i%3 == 0 ];
then
but if you introduce "==" symbol it will only produce incremental value from 1 to 20.
A beginner asking for help (:
So, I have a script that checks brackets in a text file and tells whether they are closed correctly. However, I also want to make my script print out the number of the incorrect line (where brackets are closed incorrectly). I have tried counting file lines and then making a nested while loop, however, it doesn't work for me at all ): Are there any simple solutions for this? I would like to leave the LINE counter if that's possible o:
INPUT="$1"
count=0
LINE=0
# Check if file exists
[ ! -f $INPUT ] && { echo "file $INPUT do not exist."; exit ; }
# Count file lines and read every char
while IFS= read -r LINE
do
LINE=$(( LINE + 1 ))
while read -n1 char
do
[ "$char" == "(" ] && (( count++ ))
[ "$char" == ")" ] && (( count-- ))
if [ "$count" -lt 0 ]
then
break
fi
done
done < "$INPUT"
if [ "$count" -lt 0 ]
then
echo "Found a mistake in $LINE line "
else
echo "Everything's correct"
fi
You have a couple of problems:
Your read in the inner loop consumes the input from the file, not from LINE.
The line
LINE=$(( LINE + 1 ))
is really wrong: LINE is the content of the line of your file, and your trying to add 1 to it. Weird.
Your break only breaks the inner loop (it should break two loops). Use break 2 for this.
Here's a working version of your script:
input=$1
count=0
linenb=0
# Check if file exists
[[ -f $input ]] || { echo "Error: file $input do not exist."; exit 1; }
# Count file lines and read every char
while IFS= read -r line; do
((++linenb))
while read -n1 char; do
[[ $char == '(' ]] && ((++count))
[[ $char == ')' ]] && ((--count))
((count>=0)) || break 2
done <<< "$line"
done < "$input"
if ((count<0)); then
echo "Found a mistake in line #$linenb:"
printf '%s\n' "$line"
else
echo "Everything's correct"
fi
Note that I used more ((...)) and [[...]].
I also used lowercase variable names, as your computer isn't deaf: you don't need to shout the name of the variable. (And it's nicer to the eye). And it's good practice to use lowercase variable names, as there's no chance that they clash with Bash's own variables.
Sorry about bits and snippit of information
So I am writing an average shell script program
so if use inputs
echo 1 3, .... | sh get_number
I would have to pull the numbers seperated by spaces from echo to be
var1 = 1, var2= 3, etc.
I tried
#!/bin/sh
sum=0
for i in $*
do
sum=`expr $sum + $i`
done
avg=`expr $sum / $n`
echo Average=$avg
but doesnt work....
do I include a read here?
also how would I do
sh get_number <file1>, <file2>... to grab numbers in them and sum them
in shell script?
Thanks
Sounds like you are looking for the read shell builtin:
% echo "1 2 3 4" | read a b stuff
% echo $b
2
% echo $stuff
3 4
To fix up your code:
for i in $*; do
sum=$(( sum + i ))
n=$(( n + 1 ))
done
echo "Average=$(( sum / n ))"
#!/bin/sh
while [ $# -gt 0 ]; do
(( i++ ))
(( sum += $1 ))
shift
done
echo "Average=$(( sum/i ))"
Note: This fails in dash which is the closest shell I could find to a real sh.
An example of reading values from files passed as command line arguments or from lines read from stdin:
add_to_sum() {
set $*
while [ $# -gt 0 ]; do
I=`expr $I + 1`
SUM=`expr $SUM + $1`
shift
done
}
I=0
SUM=0
if [ $# -gt 0 ]; then
# process any arguments on the command line
while [ $# -gt 0 ]; do
FILE=$1
shift
while read LINE; do
add_to_sum "$LINE"
done < "$FILE"
done
else
# if no arguments on the command line, read from stdin
while read LINE; do
add_to_sum "$LINE"
done
fi
# be sure not to divide by zero
[ $I -gt 0 ] && echo Average=`expr $SUM / $I`