The file command can make a guess about a file’s content and return a description about the identified file type:
file blank1
blank1: empty
file file1
file1: ASCII text
You can include the names of more than one file in a space separated list files in order to test multiple files in a single command:
file blank1 file1 text1
blank1: empty
file1: ASCII text
text1: ASCII text
Using * as the filename will return a list for all files in the working directory:
file *
blank1: empty
blank2: empty
blank3: empty
blank4: empty
blank5: empty
file1: ASCII text
file2: ASCII text
file3: ASCII text
file4: ASCII text
file5: ASCII text
text1: ASCII text
text2: ASCII text
text3: ASCII text
text4: ASCII text
text5: ASCII text