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This article explains how to sort data based on the second column of a file in bash.

Overview of the Sort Command in Bash

Sort files using the sort command, which places records in a specific order. By default, the sort command sorts files assuming that they contain ASCII data.

Numeric sorting is another option available through the sort command. The sort command includes the following functions:

1. Lines that begin with a number appear before lines that begin with a letter.
2. Lines that begin with letters later in the alphabetical order appear after lines that begin with earlier letters.
3. Lines that begin with an uppercase letter appear before lines that begin with the same lowercase letter.

Suppose we create a data file named filename.csv and open the file in bash using cat command.

The syntax to open a file in Bash is:

$ cat filename.csv

Sort mixed case, uppercase, and lowercase files: In a mixed case file, uppercase letters are sorted first, followed by lowercase characters.

There are several options for sorting, including:

• -k - This option helps to sort the data based on any specified column. For example, parameter -k5 will start sorting from the fifth field of each line instead of the fifth character of each line (note here the columns are defined as comma separated fields).
• -n - This option specifies numeric sorting, which means that the column should be read as a row of numbers rather than text.
• -r - Sort order is the opposite of the -r option. Another way to write it is `-reverse.
• -i - This option ignores non-printing characters. Another way to write it is -ignore-nonprinting.
• -b - This option ignores leading spaces, which is useful since line numbers are counted using spaces. Another way to write this is ignore-leading-blanks.
• -f - This option ignores case, A==a. Another way to write it is to ignore case. This option causes the preprocessor to use operators other than space: -t [新分隔符].

  Another way to write it is -field-separator.

Sort data based on the second column of a file in Bash

Using the -k option, sort enables us to sort a file by columns. Let's start by creating a file with multiple columns. In the sort, a single space is used to separate each column.

For example, we have used -k 2 to sort the second column. We have created a file called filename.csv. The data available in the file is as follows:

Bonie,22
Julie,23
Henry,15
Flamingo,34
Peter,11

Use the cat command to view the items in the file before sorting.

$ cat filename.csv

Output:

Bonie,22
Julie,23
Henry,15
Flamingo,34
Peter,11

Syntax to sort data based on the second column of a file in Bash:

sort -k2 -n filename.csv

Output after sorting the second column:

Bonie,22
Flamingo,34
Henry,15
Julie,23
Peter,11