Run a bash for loop zero times [duplicate]

Question

For a c-style language for loop the following executes zero times:

for (int myvar = 0; myvar <= -3; myvar++) {
   printf("hi")
}

bash instead will execute the loop four times by going by -1

for j in {0..-3}; do echo 'hi'; done

hi
hi
hi
hi

The following will execute once

for j in {1..4..0}; do echo 'hi'; done

hi

So how to avoid executing the loop short of commenting the entire thing out? I'd like to control this via variables in the loop indices:

first=0
last=-3
step=1
for j in {$first..$last..$step}; do echo 'hi'; done

hi

The first loop you posted will actually produce a syntax error. — user1934428
– user1934428, Commented May 9, 2022 at 6:54

pjh · Accepted Answer · 2022-05-09 00:56:47Z

4

for ((j=0; j<=-3; j++)); do
    echo hi
done

for ((j=first; j<=last; j+=step)); do
    echo hi
done

answered May 9, 2022 at 0:56

pjh

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1 Comment

Oh bash has the c-style looping (albeit with slightly different syntax)