Send output to multiple commands using tee utility and bash process substitution.
Use this method to perform a different set of operations on the same input data.
$ cat /etc/passwd | tee >(echo "All accounts: $(wc -l)") >(echo "User accounts: $(grep -c -v "false|nologin"$)") >(echo "System accounts: $(grep -c "false|nologin"$)") &>/dev/null
System accounts: 51 User accounts: 4 All accounts: 55
Use this method to extract interesting information from a single data source.
$ tail -f /var/log/syslog | tee >(grep --color "systemd\[.*\]:") >(grep --color "dhclient\[[0-9]*\]") &>/dev/null Mar 16 21:33:40 milosz-XPS-13-9343 dhclient[5956]: bound to 192.168.88.240 -- renewal in 275 seconds. Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Starting Network Manager Script Dispatcher Service... Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Started Network Manager Script Dispatcher Service.
Use this method to extract interesting information from a single data source and store it using files.
$ tail -f /var/log/syslog | tee \
>(stdbuf --output=0 grep "systemd\[.*\]:" | tee /tmp/syslog-systemd.log) \
>(stdbuf --output=0 grep "dhclient\[[0-9]*\]:" | tee /tmp/syslog-dhclient.log) \
&>/dev/null
Mar 16 21:33:40 milosz-XPS-13-9343 dhclient[5956]: bound to 192.168.88.240 -- renewal in 275 seconds.
Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Starting Network Manager Script Dispatcher Service...
Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Started Network Manager Script Dispatcher Service.
Verify file contents.
$ cat /tmp/syslog-dhclient.log
Mar 16 21:33:40 milosz-XPS-13-9343 dhclient[5956]: bound to 192.168.88.240 -- renewal in 275 seconds.
$ cat /tmp/syslog-systemd.log
Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Starting Network Manager Script Dispatcher Service... Mar 16 21:33:40 milosz-XPS-13-9343 systemd[1]: Started Network Manager Script Dispatcher Service.
