mjhjmtu

What is wrong with this cmd line (Centos 7):

if (grep ssl_certificate /etc/nginx/conf.d/platform.conf)
then echo $(grep ssl_certc /etc/nginx/conf.d/file.conf) > /etc/nginx/conf.d/file-certs.conf
fi

In file.conf there are 2 lines with ssl_certificate and ssl_certificate_key.
It should move existing SSL certificates from /etc/nginx/conf.d/file.conf to /etc/nginx/conf.d/file-certs.conf.

There is nothing syntactically wrong with the code fragment, but it is unusual.

To test whether a string is found in a file using grep, and do something if that is the case, use

if grep -qwF ssl_certificate /etc/nginx/conf.d/platform.conf; then

The options -q, -w and -F will make grep quiet (-q) and will match the given pattern as a fixed string rather than as a regular expression (-F). Furthermore, -w will make grep look for a complete word. In this case, the string ssl_certificate3 would not match the pattern.

grep will return a zero exit status if the string was found in the file, and the body of the if statement would be executed.

The statement

echo $(somecommand)

is a bit useless.

The command substitution $(somecommand) will be replaced by the output of somecommand and the shell will perform word splitting and filename generation on the resulting string (which is likely unwanted). Using this with echo is useless in the sense that you could just have done

somecommand

The complete if statement:

if grep -qwF ssl_certificate /etc/nginx/conf.d/platform.conf; then
 grep -wF ssl_certc /etc/nginx/conf.d/file.conf >/etc/nginx/conf.d/file-certs.conf
fi

(This assumes that ssl_certc is a complete word. Remove -w from that grep otherwise)

Alternatively, using short circuit syntax,

grep -qwF ssl_certificate /etc/nginx/conf.d/platform.conf &&
grep -wF ssl_certc /etc/nginx/conf.d/file.conf >/etc/nginx/conf.d/file-certs.conf

Note that this will overwrite the contents of /etc/nginx/conf.d/file-certs.conf if that file exists. Change > to >> to append to the file instead, if overwriting is not intended.