rafind2 is the command line front-end of the searching library in radare2. These commands are equivalent to the / (searching) module. For more information on searching, see the Searching page.
String Searching
We can search for strings using the -s flag. This will search for a specific string and return the offset from the base address.
$ rafind2 -s "flag.txt" ~/args
0x2016
Use the -z flag to search for all zero-terminated strings. This will return the address and the string.
Use the -e flag to search for a regular expression. This will return the address and the string. Remember that radare2 uses / for edge wildcards and .. for centered wildcards.