New to bash I was trying to write simple while loop:
let i = $1
while(i < 4); do
echo Hi
((i++))
done
Running this with: $ bash bash_file.sh 0
Gave me this warning
bash_file.sh line 2: 4: no such file or directory
Question: since when a variable must be file or directory?
How to solve this?
EDIT: if I want to loop while i < $1 + $2, when $1 and $2 are numbers, how to write it>
You need an arithmetic statement (two parentheses), not a subshell. let is unnecessary here.
i=$1
while (( i < 4 )); do
...
done
while's argument is a shell command. ( i < 4 ) starts a subshell which runs the command i, reading input from a file named 4. The redirection is processed before the command is looked up, which explains why you don't get a i: command not found error.
You can simply replace 4 with the expression you want to use:
while (( i < $1 + $2 )); do
let is unnecessary here. You are using let... (( i < 4 ))
let i=$1 is unnecessary; ((...)) is basically the same as let, but as a distinct syntactic structure it can be parsed differently (no need to quote * or whitespace, for instance).i=$1
while [ "$i" -le 4 ]
do
echo $i
i=$((i+1))
done
More about bash conditions: https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Looping-Constructs
