SIMPLEST SOLUTION
awk -F',' '$7 ~ /-99/ {print $0}' filename.csv > result.csv
1. Please note that ',' defines your separator to be comma.
2. $ defines column.
so, $7 defines the column number which you want to have a special value. here 7.
3.  ~ /-99/ searches for -99. you might put anything you need.
4.  $0 stands for ALL the columns in the file. You could simply write $1","$2","...... if you do not want to print only specific columns.(or $1$2... if you do not need comma as separator for your results)
awk -F',' '$7 ~ /-99/ {print $0}' filename.csv > result.csv
5.   > result.csv saves the output instead of printing it in terminal in result.scv file.
Please note that
','defines your separator to be comma.$defines column. so,$7defines the column number which you want to have a special value. here7.~ /-99/searches for-99. you might put anything you need.$0stands for ALL the columns in the file. You could simply write$1","$2","......if you do not want to print only specific columns.(or$1$2...if you do not need comma as separator for your results)> result.csvsaves the output instead of printing it in terminal inresult.scvfile.