Error when i try to use if in the for loop in bash

Question

I have a problem when i try to run a for loop in a for loop.

I try to make 24 files with ips with step of 10.

To explain more in the first file i need to have all ips that ends betwen 1-10 and second 11 to 20 and so on.

I try to use:

    for i in {1..240}
    do
    for r in {1..24}
    do
        if [ "$i" -le "$r0" ]
        then
            echo "4.2.2.$i" >> "server-$r"
        fi
    done
done

The error i recived is when i run bash -xv script_name:

script_name: line 5: [: : integer expression expected
+ for r in '{1..24}'
+ '[' 240 -le '' ']'
script_name: line 5: [: : integer expression expected
+ for r in '{1..24}'
+ '[' 240 -le '' ']'
script_name: line 5: [: : integer expression expected

The filenames are server-$r, ie server-1,server-2, so on until server-24

Any advice?

Thank you.

devnull · Accepted Answer · 2014-01-31 13:18:16Z

3

The error is in the following:

if [ "$i" -le "$r0" ]

You don't have a variable r0, which causes the error. Say:

if [ "$i" -le "${r}0" ]

instead so as to avoid ambiguity.

Since you wanted to multiply the number by 10, you could write it mathematically as:

if [ "$i" -le $((r*10)) ]

or even

(( i <= r*10 ))

edited Jan 31, 2014 at 13:18

answered Jan 31, 2014 at 8:45

devnull

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2 Comments

chepner Over a year ago

The $((...)) is redundant inside ((...)): (( i <= r*10 )).

MiddleCloud Over a year ago

It's woking, but in the files i found progresiv all the ips, not just those 10 ips. in 1st are 1 to 10 in secod 1 to 20 and the final 1 to 240. How can i limit just 10 of the ips.

Charles Duffy · Accepted Answer · 2014-01-31 13:41:27Z

1

This isn't the bash-native / idiomatic way to do things anyhow.

for ((i=1; i<=240; i++)); do
    for ((r=1; r<=24; r++)); do
        if (( i <= (r * 10) )); then
            echo "4.2.2.$i"
        fi
    done >"server-$r"
done

Opening the server-$r file only once per value of $r is far more efficient than opening it for each individual echo (otherwise you're opening and closing the file every time it needs to be accessed), and using expansions such as {1..3} is inflexible (only supported with literal numbers, not variables) and expands to a wordlist that gets iterated over, thus using more memory than using a C-style for loop.

answered Jan 31, 2014 at 13:41

Charles Duffy

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