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bashprintf
thor
thor

Reputation: 22560

How to include dashes in the format string of bash printf?

I'm trying to concatenate strings in bash using printf by following the examples here:

$ printf "%s " "hello printf" "in" "bash script"

The above works. But when I try to add to the format string some dashes (-):

$ printf "--file=%s " "hello printf" "in" "bash script"

it generates an error:

sh: printf: --: invalid option

Obviously, it's treating the format string as an option. How can I include dashes - into the output?

(I tried to add use \- to escape the dashes, to no avail.)

Upvotes: 10

Views: 4342

Answers (1)

Inian
Inian

Reputation: 85895

Always specify end of command line flags when using strings involving --. In general the shell commands need to know where their positional argument start at. So by forcing -- after printf we let it know that the subsequent arguments are to be interpreted as its arguments. At this point, afterwards using -- will be treated literally instead of being considered as a command line switch.

so define your printf as

printf -- "--file=%s " "hello printf" "in" "bash script"

Also if you are planning to specify multiple printf argument strings,do not include them in same format specifier. You might need this

printf -- "--file=%s %s %s" "hello printf" "in" "bash script"

See more on The printf command in bash

Upvotes: 12

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