#Bash 的 join 命令
join [OPTION]... FILE1 FILE2
功能
将两个文件中的行按照公共字段连接。
类型
可执行文件（/usr/bin/join），属于 coreutils。
参数
OPTION选项：-1 FIELD-FILE1根据FIELD字段进行匹配-2 FIELD-FILE2根据FIELD字段进行匹配-a FILENUM-FILENUM取 1 或 2，表示FILE1或FILE2，额外打印对应文件中不可配对的行-e STRING- 使用STRING填补缺失的空行-i,--ignore-case- 比较字段时忽略大小写-j FIELD-FILE1和FILE2都根据FIELD字段进行匹配-o FORMAT- 输出格式-t CHAR- 使用CHAR作为输入和输出的分隔符-v FILENUM-FILENUM取 1 或 2，表示FILE1或FILE2，仅打印对应文件中不可配对的行--check-order- 检查输入是否正确排序--nocheck-order- 不检查输入是否正确排序--header- 将每个文件的第一行视作字段标题，直接打印，不进行匹配-z,--zero-terminated- 以空字符（\0）作为行的结尾，而不是换行符（\n）--help- 显示帮助--version- 显示版本
FILE1- 要连接的文件1FILE2- 要连接的文件2
#示例
$ cat 1.txt
1 Alice
2 Bob
3 Carol
$ cat 2.txt
1 90
2 85
4 70
$ join 1.txt 2.txt # 默认按照第一列合并
1 Alice 90
2 Bob 85
$ join -a 1 1.txt 2.txt # 保留文件 1 中未匹配的行
1 Alice 90
2 Bob 85
3 Carol
$ join -a 1 1.txt 2.txt # 仅打印文件 1 中未匹配的行
3 Carol
#推荐阅读
#手册
JOIN(1) User Commands JOIN(1)
NAME
join - join lines of two files on a common field
SYNOPSIS
join [OPTION]... FILE1 FILE2
DESCRIPTION
For each pair of input lines with identical join fields, write a line
to standard output. The default join field is the first, delimited by
blanks.
When FILE1 or FILE2 (not both) is -, read standard input.
-a FILENUM
also print unpairable lines from file FILENUM, where FILENUM is
1 or 2, corresponding to FILE1 or FILE2
-e STRING
replace missing (empty) input fields with STRING; I.e., missing
fields specified with '-12jo' options
-i, --ignore-case
ignore differences in case when comparing fields
-j FIELD
equivalent to '-1 FIELD -2 FIELD'
-o FORMAT
obey FORMAT while constructing output line
-t CHAR
use CHAR as input and output field separator
-v FILENUM
like -a FILENUM, but suppress joined output lines
-1 FIELD
join on this FIELD of file 1
-2 FIELD
join on this FIELD of file 2
--check-order
check that the input is correctly sorted, even if all input
lines are pairable
--nocheck-order
do not check that the input is correctly sorted
--header
treat the first line in each file as field headers, print them
without trying to pair them
-z, --zero-terminated
line delimiter is NUL, not newline
--help display this help and exit
--version
output version information and exit
Unless -t CHAR is given, leading blanks separate fields and are ig‐
nored, else fields are separated by CHAR. Any FIELD is a field number
counted from 1. FORMAT is one or more comma or blank separated speci‐
fications, each being 'FILENUM.FIELD' or '0'. Default FORMAT outputs
the join field, the remaining fields from FILE1, the remaining fields
from FILE2, all separated by CHAR. If FORMAT is the keyword 'auto',
then the first line of each file determines the number of fields output
for each line.
Important: FILE1 and FILE2 must be sorted on the join fields. E.g.,
use "sort -k 1b,1" if 'join' has no options, or use "join -t ''" if
'sort' has no options. Note, comparisons honor the rules specified by
'LC_COLLATE'. If the input is not sorted and some lines cannot be
joined, a warning message will be given.
AUTHOR
Written by Mike Haertel.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
COPYRIGHT
Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
comm(1), uniq(1)
Full documentation <https://www.gnu.org/software/coreutils/join>
or available locally via: info '(coreutils) join invocation'
GNU coreutils 9.4 April 2024 JOIN(1)