Bash-Beginners-Guide

Bash Guide for Beginners
121script.sed
120temp_file
126test
120twolines
441txt2html.sh
kelly@octarine ~/test>
This command printed the fifth column of a long file listing, which contains the file size, and the last column,
the name of the file. This output is not very readable unless you use the official way of referring to columns,
which is to separate the ones that you want to print with a comma. In that case, the default output separater
character, usually a space, will be put in between each output field.
Local configuration
Note that the configuration of the output of the ls -l command might be different on your system.
Display of time and date is dependent on your locale setting.
6.2.2. Formatting fields
Without formatting, using only the output separator, the output looks rather poor. Inserting a couple of tabs
and a string to indicate what output this is will make it look a lot better:
kelly@octarine ~/test> ls -ldh * | grep -v total | \
awk '{ print "Size is " $5 " bytes for " $9 }'
Size is 160 bytes for orig
Size is 121 bytes for script.sed
Size is 120 bytes for temp_file
Size is 126 bytes for test
Size is 120 bytes for twolines
Size is 441 bytes for txt2html.sh
kelly@octarine ~/test>
Note the use of the backslash, which makes long input continue on the next line without the shell interpreting
this as a separate command. While your command line input can be of virtually unlimited length, your
monitor is not, and printed paper certainly isn't. Using the backslash also allows for copying and pasting of the
above lines into a terminal window.
The -h option to ls is used for supplying humanly readable size formats for bigger files. The output of a long
listing displaying the total amount of blocks in the directory is given when a directory is the argument. This
line is useless to us, so we add an asterisk. We also add the -d option for the same reason, in case asterisk
expands to a directory.
The backslash in this example marks the continuation of a line. See Section 3.3.2.
You can take out any number of columns and even reverse the order. In the example below this is
demonstrated for showing the most critical partitions:
kelly@octarine ~> df -h | sort -rnk 5 | head -3 | \
awk '{ print "Partition " $6 "\t: " $5 " full!" }'
Partition /var : 86% full!
Partition /usr : 85% full!
Partition /home : 70% full!
kelly@octarine ~>
Chapter 6. The GNU awk programming language 71