The "sort" Utility
July 19, 1998
Once you have found the files you are after using grep and
find, you often have a need to manipulate those files in special ways.
One popular tool for manipulating files is the "sort" utility. "sort"
allows you to sort the lines of a file alphabetically (according to
standard ASCII rules which means, for example, that capital letters come
before lower case letters). Check out this basic example.
![[Sort]](Images/sort.gif)
There are several useful options for sort that
are shown below.
| Option |
Explanation |
| -b |
Ignores any leading blank characters when sorting. |
| -c |
Checks to make sure that the file is not already sorted. If it
is, sort will not display anything. |
| -d |
Sorts according to letters, digits and blanks (a "dictionary" sort).
|
| -f |
Case insensitive sort. Caps and lowercases are considered the same.
|
| -i |
Ignores non printable characters. |
| +keybeg |
Defines the field to sort by. Note that field number one is "0".
|
| -keyend |
Defines the field to end the sort by. |
| -M |
Sorts as if the string is a month. Thus MAR is considered less
than SEP. |
| -n |
Specifies a numeric key. |
| -ofile |
Specifies an output file to which to write matches. |
| -r |
Specifies a reverse sort. |
| -tfld-sep |
Specifies the delimiter character for sorting fields. |
| -u |
Makes sure that duplicate items appear only once. |
Consider the following examples:
As we said, sometimes the quirks of ASCII can cause
problems when sorting. You must remember that ASCII considers capitals
before lower case letters. Thus, "Q" comes before "a" in ASCII
thinking. Thus, you will often use the -f option to sort in the
intuitive way:
![[Sort with -f]](Images/sort_ascii.gif)
Another very useful option is the field sorting option.
Using a +[number] you can sort the file according to various fields.
In the following example, we sort on last names instead of first names.
![[Sort on fields]](Images/sort_field.gif)
In the above example, sort used the space character as its field
separator. You can also specify some other character as a delimiter
such as in the following example in which we sort on the pipe (|).
Notice that we also use the -n option to sort the field according to
numerical value since ASCII sorting produces its usual
strange output (i.e.: 129 comes before 28 because 129 starts with a 1).
![[Sort on fields]](Images/sort_numeric.gif)
Finally, I don't know if you remember, but
on day one we were talking about pipelines and we gave the following
as an example:
cat directory_listing | grep .html | sort | more
Well, I return to the commands because
at this point you are finally prepared to interpret the command.
Essentially, you are cat'ing a file that ostensibly holds
a bunch of files in a directory (you might also use ls | grep....),
parsing through it looking for html files, sorting those html files
and making sure that sort only displays one screens worth of
information at once. Pretty cool eh?
The "find" Utility
Introduction to UNIX for Web Developers | Table of Contents
The "diff" Utility
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