Viewing Linux Files
with the head and tail command
Often, especially with large log files, your only interest is
in seeing the end of a file. To view just the last handful of
lines in a file, use the tail command.
$ tail
required_packages.txt
elfutils-libelf-devel-0.97.1-5.i386.rpm
glibc-headers-2.3.4-2.41.i386.rpm
glibc-kernheaders-2.4-9.1.103.EL.i386.rpm will be required as a
prerequisite
glibc-devel-2.3.4-2.41.i386.rpm
gcc-3.4.6-10.i386.rpm
libstdc++-devel-3.4.6-10.i386.rpm
gcc-c++-3.4.6-10.i386.rpm
libaio-devel-0.3.105-2.i386.rpm
sysstat-5.0.5-19.el4.i386.rpm
unixODBC-devel-2.2.11-1.RHEL4.1.i386.rpm
By default, tail displays the last 10 lines of a file. This is
a great way to look at recent entries in Oracle database alert
logs. If more than 10 lines need to be seen, specify a number of
lines as an option. For example, tail -15 required_packages.txt
will show the last 15 lines of the file required_packages.txt.
When a log file is being actively written to, like with an
alert log, displaying new lines on the screen as they are written
to the file may be preferred. To do that, add the -f option to
the tail command like this: tail -f alert_TEST.log. This allows
the monitoring of a log in near real time, though sometimes lines
may appear too quickly to read.
Of course, there will be times where the beginning of a file
rather than the end needs to be seen. For this, use the head
command.
$ head
required_packages.txt
REHEL4, OEL4:
Refer to Note 880211.1
binutils-2.15.92.0.2-25
compat-libstdc++-33-3.2.3-47.3
elfutils-libelf-0.97.1-5
glibc-2.3.4-2.41
glibc-common-2.3.4-2.41
libaio-0.3.105-2
libgcc-3.4.6-10
The head command defaults to displaying the first 10
lines of the specified file. Like with tail, the default can be
overridden and more lines or fewer lines can be displayed by
adding a number as an option. For example, head -5
required_packages.txt will display only the first five lines of
the file.
