The name of the current input file set in FILENAME variable. You can use FILENAME to display or print current input file name If no files are specified on the command line, the value of FILENAME is “-” (stdin). However, FILENAME is undefined inside the BEGIN rule unless set by getline.
How to print filename with awk
The syntax is:
awk '{ print FILENAME }' fileNameHere
awk '{ print FILENAME }' /etc/hosts
You might see file name multiple times as awk read file line-by-line. To avoid this problem update your awk/gawk syntax as follows:
awk 'FNR == 1{ print FILENAME } ' /etc/passwd
awk 'FNR == 1{ print FILENAME } ' /etc/hosts
How to print filename in BEGIN section of awk
Use the following syntax:
awk 'BEGIN{print ARGV[1]}' fileNameHere
awk 'BEGIN{print ARGV[1]}{ print "someting or do something on data" }END{}' fileNameHere
awk 'BEGIN{print ARGV[1]}' /etc/hosts
Sample outputs:
/etc/hosts
However, ARGV[1] might not always work. For example:
ls -l /etc/hosts | awk 'BEGIN{print ARGV[1]} { print }'
So you need to modify it as follows (assuming that ls -l only produced a single line of output):
ls -l /etc/hosts | awk '{ print "File: " $9 ", Owner:" $3 ", Group: " $4 }'
Sample outputs:
File: /etc/hosts, Owner:root, Group: roo
How to deal with multiple filenames specified by a wild card
Use the following simple syntax:
awk '{ print FILENAME; nextfile } ' *.c
awk 'BEGIN{ print "Starting..."} { print FILENAME; nextfile }END{ print "....DONE"} ' *.conf
Sample outputs:
Starting... blkid.conf cryptconfig.conf dhclient6.conf dhclient.conf dracut.conf gai.conf gnome_defaults.conf host.conf idmapd.conf idnalias.conf idn.conf insserv.conf iscsid.conf krb5.conf ld.so.conf logrotate.conf mke2fs.conf mtools.conf netscsid.conf nfsmount.conf nscd.conf nsswitch.conf openct.conf opensc.conf request-key.conf resolv.conf rsyncd.conf sensors3.conf slp.conf smartd.conf sysctl.conf vconsole.conf warnquota.conf wodim.conf xattr.conf xinetd.conf yp.conf ....DONE
nextfile tells awk to stop processing the current input file. The next input record read comes from the next input file. For more information see awk/gawk command man page:
man awk
man gawk