sort

sort

Sort ,  as the name suggests sorts  a file  or output of a command. Various  options  determine the sort criteria  which are called as sort keys. If multiple files are passed as parameters to sort the output of sort is concatenated.

Sorting is done in ascending lexicographic order , I e the way in which it appears in a dictionary. If a file contains numbers and alphabet both,  by default sort  places  the  sorted alphabets  first and then the numbers.

Example1)

Consider a file containing  values as shown.

/home/jones$  cat  flowers.txt

rose

lily

tulip

marigold

hibiscus

Chrysanthemum

/home/jones$  sort   flowers.txt

Chrysanthemum

hibiscus

lily

marigold

rose

tulip

If you want to sort it in reverse order ,use

/home/jones$ sort   -r  flowers.txt

tulip

rose

marigold

lily

hibiscus

Chrysanthemum

Example2)

If you want the sort to to be case insensitive sort  –f must be used.

/home/jones $  cat  flowers.txt

rose

lily

Chrysanthemum

tulip

marigold

Rose

hibiscus

chrysanthemum

To   default sort(without any option) would give

/home/jones $ Sort  flowers.txt

Chrysanthemum

Rose

Chrysanthemum

hibiscus

lily

marigold

rose

tulip

Here it sorted the letters starting with uppercase first and then  sorted  lower case ones, Now  use sort -f

/home/jones $ sort  –f  flowers.txt

Chrysanthemum

chrysanthemum

hibiscus

lily

marigold

Rose

rose

tulip

Example3)

A file may contain duplicate lines, and if you want to remove duplicate files before sorting  , use sort –u

/home/jones $ grep   error  cron.log

error code 45:invalid time

error code 35:Invalid name

error code 45:invalid time

error code 25:Invalid email-id

error code 25:Invalid email-id

error code 35 Invalid name

/home/jones $ grep   error  cron.log | sort  -u

error code 25:Invalid email-id

error code 35:Invalid name

error code 45:invalid time

Example 4)                                                                                     

You require to sort based  on  a  particular field  when they are separated by a delimiter.

/home/jones $ cat  detailed-list.csv

dolphin|mammal|12

giraffe|mammal|7

kingfisher|aves|3

moth|insecta|1

shark|fish|6

viper|reptile|2

Now,  The output of default sort command is

dolphin|mammal|12

giraffe|mammal|7

kingfisher|aves|3

moth|insecta|1

shark|fish|6

viper|reptile|2

it sorted on the basis of first field (separated by ‘|’) in alphabetic order. For a change, you required to sort it based on another column.

/home/jones$ sort  -t   “|”  +1  detailed-list.csv

kingfisher|aves|3

shark|fish|6

moth|insecta|1

dolphin|mammal|12

giraffe|mammal|7

viper|reptile|2

Here  -t  “|”  tells the sort command  do sorting on  fields  delimited by a   “|” character. If you do not use  -t option, sequence of  space  characters is considered as   default delimiter .  “+1”    instructs sort to ignore the first field or sort from second field.

Similarly if you wanted to sort it based on the third column, just using  +2  instead of +1 might not work in the given example. The output of that sort command would be as follows.

/home/jones$ sort  -t  “|”  +2  detailed-list.csv

moth|insecta|1

dolphin|mammal|12

viper|reptile|2

kingfisher|aves|3

shark|fish|6

giraffe|mammal|7

It  sorted the third  column according to its alphabetic value  and not arithmetic value. To do so you must use  -n option

/home/jones$ sort   -n  -t  “|”  +2  detailed-list.csv

moth|insecta|1

viper|reptile|2

kingfisher|aves|3

shark|fish|6

giraffe|mammal|7

dolphin|mammal|12

Example5)

The  sorting based on fields can be achieved using   sort with –k option. consider a file containing numbers.

/home/jones$ cat  num-luck

6758 987 456

2586 324 934

0437 235 417

2586 324 934

Suppose  you wanted to sort  this list  such that sorting should start from 3^rd column of 1^st field and 4^th column of  1^st  field. Here fields are separated by  one or more spaces.  Columns here refer to characters.

/home/jones$ sort   -k1.3,1.4   num-luck

2812 624 208

0437 235 417

6758 987 456

2586 324 934

To sort from 2^nd column of 1^st field and  3^rd  column of second field in reverse order,

/home/jones$ sort   -k1.2,2.3r   num-luck

2812 624 208

6758 987 456

2586 324 934

0437 235 417

Similarly, to  sort lines based on 1^st and 3^rd fields, use

Sort  –k1 –k3  <filename >

Example 6)

You may require to sort a particular file and rewrite the file with the sorted file. A simple  command of the form

Sort  filename  >new_sorted_filename     will not work and is dangerous as it  rewrites it into  an empty file. Use  sort with  –o option.

/home/jones$ sort  -o   flowers.txt    flowers.txt 

The  syntax is  sort  –o  <sorted-file>    <file>

Example 7)

Sort  uses a lot of temporary space  while sorting huge files. and by default it uses  /tmp   directory. If sufficient space was not allocated  to /tmp, then  the command would abort abruptly. so sort provides an option  -T by which you can  use an alternative directory  for storing temporary files.

The sort command  sort  -t   “|”  +1  detailed-list.csv in example 4 can be written as

sort  -t   “|”  +1   -T   /backup/jones     detailed-list.csv.

this will use  /backup/jones    directory   for storing temporary files.