mysqldump - redirect greped STDERR to a file

Question

mysqldump generates STDOUT (used to dump *.sql), and also generates STDERR - that I need to filter + write to a file.

mysqldump --user=db_username --password=db_password --add-drop-database --host=db_host db_name 2>> '/srv/www/data_appsrv/logs/mysql_date_ym.log' > '/mnt/backup_srv/backup/daily/file_nm.sql'

The code above will write STDERR to mysql_date_ym.log

I need to exclude Warning: Using a password string from STDERR that is written to mysql_date_ym.log

I tried variations with grep, 2>> and >, but none works.

Answer 1

This should work

command 1>stdout.txt 2> >(grep -v "Thing to remove from stderr" >stderr.txt)

Which will redirect STDOUT to stdout.txt, and STDERR via process substitution into the grep filter, then finally to stderr.txt.

So your full command would look like this

mysqldump --user=db_username --password=db_password --add-drop-database --host=db_host db_name 1>'/mnt/backup_srv/backup/daily/file_nm.sql' 2> >(grep -v "Warning: Using a password" > '/srv/www/data_appsrv/logs/mysql_date_ym.log')

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You could also use a sed script to run on the mysql_date_ym.log file after redirecting STDOUT/STDERR normally to the output files.

sed -i 's/Warning: Using a password//g' mysql_date_ym.log