File permission Related:

To change file permissions for all the files in a directory 

$ chmod 755 * 

To copy the file having spaces in its file name 

EX: 1)Filename is Supplier Key Contacts.xls 

Here there are spaces between file name. 

cp "Supplier Key Contacts.xls" "Supplier Key Contacts.xls_bkp"  

To find and replace a string in one or more files in a directory 

perl -pi -e 's/old_string/new_string/g' file_pattern 

EX:- perl -pi -e 's/18791/7001/g' *.sh