Repeating a character using printf and outputting to variable

Question

I'm having trouble making a string out of repeated single characters. This works when I'm not assigning it to a variable:

printf "*%.0s" $(seq 1 $(expr $1 / 2))

This just assigns the script name to test:

printf -v test "*%.0s" $(seq 1 $(expr $1 / 2))

I also tried:

test=$(printf "*%.0s" $(seq 1 $(expr $1 / 2)))

But it does the same thing.

Why doesn't this work, and is there another way to build a string and assign it to a variable?

I'm expecting test to contain $1 / 2 asterisks. (i.e. "****" if $1 / 2 results in 4) — baiumbg
– baiumbg, Commented Nov 26, 2015 at 11:18
I tried that as well, but my variable still just contained my script name. I tried test=$(echo "${testprep// /*}") — baiumbg
– baiumbg, Commented Nov 26, 2015 at 12:49
What's the problem with printf -v test "*%.0s" $(seq 1 $(expr $1 / 2)) code? It works fine for me. — anubhava
– anubhava, Commented Nov 26, 2015 at 12:50

chepner · Accepted Answer · 2015-11-26 13:04:11Z

1

The value of test is fine; you just need to quote its expansion:

echo "$test"

Otherwise, the asterisks in the value are expanded to the contents of the current directory via pathname expansion.

answered Nov 26, 2015 at 13:04

chepner

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6 Comments

sjsam Over a year ago

What if we have more than one asterisk? Shouldn't all of them be expanded ?

chepner Over a year ago

As a single pattern, each additional asterisk is redundant. How it is explicitly interpreted is a matter of implementation, but conceptually each asterisk matches some substring of the final result. For example, *** could match foo with each asterisk matching a single letter, or the first asterisk matching foo and the others matching empty strings, etc.

sjsam Over a year ago

val=$(expr $1 / 2);s=$(printf "%-${val}s" "$2");test=$(echo "${s// /$2}"); echo "${test}"; I prepared this general solution for OPs problem. But not sure it it will work for all the inputs though. Works like ./somescript 30 * or ./somescript 30 \\

baiumbg Over a year ago

Thanks! I knew it would come down to something very simple. The general solution might come in handy as well.

sjsam Over a year ago

@baiumbg : Please test it thoroughly though and remember to escape the escape sequences ;)

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