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join(1): Add EXAMPLES section

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Add EXAMPLES covering options -e, -o, -t, -v, -1

Approved by:	0mp@
Differential Revision: https://reviews.freebsd.org/D25186
This commit is contained in:
Fernando Apesteguía 2020-06-20 11:27:59 +00:00
parent f3ec6af0e4
commit 69ad6e739b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=362436
1 changed files with 73 additions and 1 deletions
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74
usr.bin/join/join.1
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@ -31,7 +31,7 @@
.\" @(#)join.1 8.3 (Berkeley) 4/28/95
.\" $FreeBSD$
.\"
.Dd July 5, 2004
.Dd June 20, 2020
.Dt JOIN 1
.Os
.Sh NAME
@ -164,6 +164,78 @@ is
the standard input is used.
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Assuming a file named
.Pa nobel_laureates.txt
with information about some of the first Nobel Peace Prize laureates:
.Bd -literal -offset indent
1901,Jean Henri Dunant,M
1901,Frederic Passy,M
1902,Elie Ducommun,M
1905,Baroness Bertha Sophie Felicita Von Suttner,F
1910,Permanent International Peace Bureau,
.Ed
.Pp
and a second file
.Pa nobel_nationalities.txt
with their nationalities:
.Bd -literal -offset indent
Jean Henri Dunant,Switzerland
Frederic Passy,France
Elie Ducommun,Switzerland
Baroness Bertha Sophie Felicita Von Suttner
.Ed
.Pp
Join the two files using the second column from first file and the default first
column from second file specifying a custom field delimiter:
.Bd -literal -offset indent
$ join -t, -1 2 nobel_laureates.txt nobel_nationalities.txt
Jean Henri Dunant,1901,M,Switzerland
Frederic Passy,1901,M,France
Elie Ducommun,1902,M,Switzerland
Baroness Bertha Sophie Felicita Von Suttner,1905,F
.Ed
.Pp
Show only the year and the nationality of the laureate using
.Ql <<NULL>>
to replace empty fields:
.Bd -literal -offset indent
$ join -e "<<NULL>>" -t, -1 2 -o "1.1 2.2" nobel_laureates.txt nobel_nationalities.txt
1901,Switzerland
1901,France
1902,Switzerland
1905,<<NULL>>
.Ed
.Pp
Show only lines from first file which do not have a match in second file:
.Bd -literal -offset indent
$ join -v1 -t, -1 2 nobel_laureates.txt nobel_nationalities.txt
Permanent International Peace Bureau,1910,
.Ed
.Pp
Assuming a file named
.Pa capitals.txt
with the following content:
.Bd -literal -offset indent
Belgium,Brussels
France,Paris
Italy,Rome
Switzerland
.Ed
.Pp
Show the name and capital of the country where the laureate was born.
This example uses
.Pa nobel_nationalities.txt
as a bridge but does not show any information from that file.
Also see the note about
.Xr sort 1
above to understand why we need to sort the intermediate result.
.Bd -literal -offset indent
$ join -t, -1 2 -o 1.2 2.2 nobel_laureates.txt nobel_nationalities.txt | \e
sort -k2 -t, | join -t, -e "<<NULL>>" -1 2 -o 1.1 2.2 - capitals.txt
Elie Ducommun,<<NULL>>
Jean Henri Dunant,<<NULL>>
.Ed
.Sh COMPATIBILITY
For compatibility with historic versions of
.Nm ,