How to display content of files along with file names?

Sometimes it is useful to display content of files along with file names. egrep or pr can do the trick


$ cat 1.txt
0
1

$ cat 2.txt
2
3

#==cat can't display file name

$ cat *.txt
0
1
2
3

#==display all with wildcard filter *

$ egrep \* *.txt
1.txt:0
1.txt:1
2.txt:2
2.txt:3

#==The header of pr displays filename, sed is used to chop blank lines

$ pr *.txt sed '/^$/d'
2009-03-25 03:17 1.txt Page 1
0
1
2009-03-25 03:17 2.txt Page 1
2
3