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.)
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
%s is intentional, I'm guessing. printf will repeat the format string if there are extra arguments. "--file=%s " a b c produces --file=a --file=b --file=c.
for f in "hello printf" "in" "bash script"; do args+=(--file "$f") rather than printf at all."--file=%q " would also work. Though an array is better.