Unix - find and remove files

Since rm command does not support searching of files we need to use find and rm command in combination. While working with searching and removing files today, I thought, I will share with you some of these combinations to make your search easy.

find

Search files matching a certain pattern viz, '&'

find . -name "*&*"

Here we are looking in the current directory for all the files which have '&' in its name and in case you need to exclude few set of files with a particular pattern viz, '_'

find . -name "*&*" -and –not –name "_"

If the directory we are searching in also has subdirectories which you would like to exclude from the search, then use type switch,

find . –type f -name "*&*" -and –not –name "_"

find and rm

Now that we have found the list of files we would like to remove from the directory, we need to pass this list to the 'rm' (remove) command. Since rm command takes one file at a time, there are two ways we can do this.

find . -name "FILE_SEARCH_PATTERN"-exec rm -i {} \;

If you don't want the confirmation before removing each file, replace the rm switch –i with -f

Or

find . -name "FILE_SEARCH_PATTERN" | xargs rm

Where 'xargs' creates an argument list for a UNIX command using standard input and executes it. In UNIX shells, there is a restriction on the number of arguments allowed on a command line. 'xargs' helps here with bundling the arguments into smaller groups and execute rm command for each group separately.

Append rows to the SELECT query result

Something I stumped over recently when I was working with a list of categories. Simply put, I had to sort the category on the number of questions each have and append category 'Other' at the end.

UNION ALL can help resolve this issue. So All we need to do is-

SELECT category
FROM t_question
WHERE category <> 'other'
GROUP BY category

UNION all

SELECT DISTINCT category
FROM t_question
WHERE category = 'other'


which will give me the list of categories from the table and add category 'other' at the end of the list. But if you need to sort the list (ORDER BY) as I needed to and if you are working on MS SQL Server 2005 then ORDER BY clause does not work with UNION clause.

SO I updated the above query to-

SELECT c.category
FROM (SELECT category, count(*) num
FROM t_question
              WHERE category <> 'other'
              GROUP BY category

              UNION all

              SELECT DISTINCT category, 1
              FROM t_question
              WHERE category = 'other') c 
ORDER BY num DESC


In case you bump into the same issue, now you know how to tweak your query.