Linux Admin - tee Command

tee is a simple command, letting an administrator write command output and view a file at the same time. This simple command can save time over first writing stdout to a file, then viewing the file contents.

Following are the common Switches used with tee.

Without tee to both view and write files and directories in /etc, where each begins with the letter "a".

[root@centosLocal Documents]# ls -d /etc/a*
/etc/abrt     /etc/aliases.db    /etc/anacrontab   /etc/at-spi2  /etc/autofs.conf
/etc/auto.master.d  /etc/auto.smb  /etc/adjtime  /etc/alsa      /etc/asound.conf
/etc/audisp         /etc/autofs_ldap_auth.conf  /etc/auto.misc  /etc/avahi
/etc/aliases  /etc/alternatives  /etc/at.deny   /etc/audit   /etc/auto.master
/etc/auto.net
[root@centosLocal Documents]# ls -d /etc/a* > ./etc_report_a.txt
[root@centosLocal Documents]# cat ./etc_report_a.txt
/etc/abrt
/etc/adjtime
/etc/aliases
/etc/aliases.db
/etc/alsa
/etc/alternatives 
/etc/anacrontab 
/etc/asound.conf 
/etc/at.deny 
/etc/at-spi2 
/etc/audisp 
/etc/audit 
/etc/autofs.conf 
/etc/autofs_ldap_auth.conf 
/etc/auto.master 
/etc/auto.master.d 
/etc/auto.misc 
/etc/auto.net 
/etc/auto.smb
/etc/avahi

[root@centosLocal Documents]#

This small task is much more efficient with the tee command.

[root@centosLocal Documents]# ls -d /etc/a* | tee ./etc_report_a.txt 
/etc/abrt 
/etc/adjtime 
/etc/aliases 
/etc/aliases.db 
/etc/alsa 
/etc/alternatives 
/etc/anacrontab 
/etc/asound.conf 
/etc/at.deny 
/etc/at-spi2 
/etc/audisp 
/etc/audit 
/etc/autofs.conf 
/etc/autofs_ldap_auth.conf 
/etc/auto.master 
/etc/auto.master.d 
/etc/auto.misc 
/etc/auto.net 
/etc/auto.smb 
/etc/avahi

[root@centosLocal Documents]#