I frequently write for-loops in bash with the well-known syntax:
for i in {1..10} [...]
Now, I'm trying to write one where the top is defined by a variable:
TOP=10
for i in {1..$TOP} [...]
I've tried a variety of parens, curly-brackets, evaluations, etc, and typically get back an error "bad substitution".
How can I write my for-loop so that the limit depends on a variable instead of a hard-coded value?
You can use for loop like this to iterate with a variable $TOP:
for ((i=1; i<=$TOP; i++))
do
echo $i
# rest of your code
done
If you have a gnu system, you can use seq to generate various sequences, including this.
for i in $(seq $TOP); do
...
done
Answer is partly there : see Example 11-12. A C-style for loop.
Here is a summary from there, but be aware the final answer to your question depends on your bash interpreter (/bin/bash --version):
# Standard syntax.
for a in 1 2 3 4 5 6 7 8 9 10
# Using "seq" ...
for a in `seq 10`
# Using brace expansion ...
# Bash, version 3+.
for a in {1..10}
# Using C-like syntax.
LIMIT=10
for ((a=1; a <= LIMIT ; a++)) # Double parentheses, and "LIMIT" with no "$".
# another example
lines=$(cat $file_name | wc -l)
for i in `seq 1 "$lines"`
# An another more advanced example: looping up to the last element count of an array :
for element in $(seq 1 ${#my_array[@]})
