The

rm "$OUTPUT/*.gz"

shell command line tells the shell to execute /bin/rm with with two arguments: rm and /path/to/backup/files/*.gz.

The space, " and $ are special characters in the shell language syntax. Space is used to delimit command arguments, " is used to quote other special characters (not all, $ for instance is still special) like that * above, and $ is used for some expansions (like the $OUTPUT parameter expansion that you're using here).

rm once started will try to remove that /path/to/backup/files/*.gz file. If that file doesn't exist (as is the case for you), it will report an error.

When you write:

rm /path/to/backup/files/*.gz

or

rm "$OUTPUT"/*.gz

Since * is not quoted this time, it triggers another special feature of the shell called globbing or filename generation or filename expansion. The shell tries to expand the word that contains that * character to the list of file names that match the pattern.

So if /path/to/backup/files contains a a.gz and b.gz files, the shell will actually call rm with 3 arguments: rm, /path/to/backup/files/a.gz and /path/to/backup/files/b.gz which looks more like what you want here.

Note that $OUTPUT itself still needs to be quoted as otherwise it could end up being split if it contains characters of $IFS or also be subject to globbing if it contained any wildcard characters (like that * above).

It's also a good idea to get used to writing:

rm -- "$OUTPUT"/*.gz

Here $OUTPUT happens to start with /, so it's fine, but the day you change $OUTPUT to -foo- for instance, it will stop working as that -foo-/... would be taken by rm as options.

If the script is not meant to be interactive, you may want to add the -f option to rm. That will disable all user prompts, and remove the error if there's no matching file (most shells, when a glob has no match, pass the pattern as-is to the application, and rm -f doesn't complain when asked to remove a file that doesn't exist in the first place).

The

rm "$OUTPUT/*.gz"

shell command line tells the shell to execute /bin/rm with with two arguments: rm and /path/to/backup/files/*.gz.

The space, " and $ are special characters in the shell language syntax. Space is used to delimit command arguments, " is used to quote other special characters (not all, $ for instance is still special) like that * above, and $ is used for some expansions (like the $OUTPUT parameter expansion that you're using here).

rm once started will try to remove that /path/to/backup/files/*.gz file. If that file doesn't exist (as is the case for you), it will report an error.

When you write:

rm /path/to/backup/files/*.gz

or

rm "$OUTPUT"/*.gz

Since * is not quoted this time, it triggers another special feature of the shell called globbing or filename generation or pathname expansion. The shell tries to expand the word that contains that * character to the list of file names that match the pattern.

So if /path/to/backup/files contains a a.gz and b.gz files, the shell will actually call rm with 3 arguments: rm, /path/to/backup/files/a.gz and /path/to/backup/files/b.gz which looks more like what you want here.

Note that $OUTPUT itself still needs to be quoted as otherwise it could end up being split if it contains characters of $IFS or also be subject to globbing if it contained any wildcard characters (like that * above).

It's also a good idea to get used to writing:

rm -- "$OUTPUT"/*.gz

Here $OUTPUT happens to start with /, so it's fine, but the day you change $OUTPUT to -foo- for instance, it will stop working as that -foo-/... would be taken by rm as options.

If the script is not meant to be interactive, you may want to add the -f option to rm. That will disable all user prompts, and remove the error if there's no matching file (many shells, when a glob has no match, pass the pattern as-is to the application, and rm -f doesn't complain when asked to remove a file that doesn't exist in the first place).

The

rm "$OUTPUT/*.gz"

shell command line tells the shell to execute /bin/rm with with two arguments: rm and /path/to/backup/files/*.gz.

The space, " and $ are special characters in the shell language syntax. Space is used to delimit command arguments, " is used to quote other special characters (not all, $ for instance is still special) like that *above, and$is used for some expansions (like the$OUTPUT` parameter expansion that you're using here.

rm once started will try to remove that /path/to/backup/files/*.gz file. If that file doesn't exist (as is the case for you), it will report an error.

When you write:

rm /path/to/backup/files/*.gz

or

rm "$OUTPUT"/*.gz

Since * is not quoted, it triggers another special feature of the shell called globbing or filename expansion. The shell tries to expand the word that contains that * character to the list of file names that match the pattern.

So if /path/to/backup/files countains a a.gz and b.gz files, the shell will actually call rm with 3 arguments: rm, /path/to/backup/files/a.gz and /path/to/backup/files/b.gz which looks more like what you want here.

The

rm "$OUTPUT/*.gz"

shell command line tells the shell to execute /bin/rm with with two arguments: rm and /path/to/backup/files/*.gz.

The space, " and $ are special characters in the shell language syntax. Space is used to delimit command arguments, " is used to quote other special characters (not all, $ for instance is still special) like that * above, and $ is used for some expansions (like the $OUTPUT parameter expansion that you're using here).

rm once started will try to remove that /path/to/backup/files/*.gz file. If that file doesn't exist (as is the case for you), it will report an error.

When you write:

rm /path/to/backup/files/*.gz

or

rm "$OUTPUT"/*.gz

Since * is not quoted this time, it triggers another special feature of the shell called globbing or filename generation or filename expansion. The shell tries to expand the word that contains that * character to the list of file names that match the pattern.

So if /path/to/backup/files contains a a.gz and b.gz files, the shell will actually call rm with 3 arguments: rm, /path/to/backup/files/a.gz and /path/to/backup/files/b.gz which looks more like what you want here.

Note that $OUTPUT itself still needs to be quoted as otherwise it could end up being split if it contains characters of $IFS or also be subject to globbing if it contained any wildcard characters (like that * above).

It's also a good idea to get used to writing:

rm -- "$OUTPUT"/*.gz

Here $OUTPUT happens to start with /, so it's fine, but the day you change $OUTPUT to -foo- for instance, it will stop working as that -foo-/... would be taken by rm as options.

If the script is not meant to be interactive, you may want to add the -f option to rm. That will disable all user prompts, and remove the error if there's no matching file (most shells, when a glob has no match, pass the pattern as-is to the application, and rm -f doesn't complain when asked to remove a file that doesn't exist in the first place).