Join lines on a common field, writes to standard output a line for each pair of input lines that have identical join fields.
SYNTAX join [Options]... File1 File2
Either FILE1 or FILE2 (but not both) can be `-', meaning standard input. FILE1 and FILE2 should be already sorted in increasing textual order on the join fields, using the collating sequence specified by the `LC_COLLATE' locale.
Unless the `-t' option is given, the input should be sorted ignoring blanks at the start of the join field, as in `sort -b'. If the `--ignore-case' option is given, lines should be sorted without regard to the case of characters in the join field, as in `sort
The defaults are:
The join field is the first field in each line;
Fields in the input are separated by one or more blanks, with leading blanks on the line ignored;
Fields in the output are separated by a space;
Each output line consists of the join field, the remaining fields from FILE1, then the remaining fields from FILE2.
OPTIONS -a FILE-NUMBER Print a line for each unpairable line in file FILE-NUMBER (either `1' or `2'), in addition to the normal output. -e STRING Replace those output fields that are missing in the input with STRING. -i --ignore-case Ignore differences in case when comparing keys. With this option, the lines of the input files must be ordered in the same way. Use `sort -f' to produce this ordering. -1 FIELD -j1 FIELD Join on field FIELD (a positive integer) of file 1. -2 FIELD -j2 FIELD Join on field FIELD (a positive integer) of file 2. -j FIELD Equivalent to `-1 FIELD -2 FIELD'. -o FIELD-LIST... Construct each output line according to the format in FIELD-LIST. Each element in FIELD-LIST is either the single character `0' or has the form M.N where the file number, M, is `1' or `2' and N is a positive field number. A field specification of `0' denotes the join field. In most cases, the functionality of the `0' field spec can be reproduced using the explicit M.N that corresponds to the join field. However, when printing unpairable lines (using either of the `-a' or `-v' options), there is no way to specify the join field using M.N in FIELD-LIST if there are unpairable lines in both files. To give `join' that functionality, POSIX invented the `0' field specification notation. The elements in FIELD-LIST are separated by commas or blanks. Multiple FIELD-LIST arguments can be given after a single `-o' option; the values of all lists given with `-o' are concatenated together. All output lines - including those printed because of any -a or -v option - are subject to the specified FIELD-LIST. -t CHAR Use character CHAR as the input and output field separator. -v FILE-NUMBER Print a line for each unpairable line in file FILE-NUMBER (either `1' or `2'), instead of the normal output.
"A nation is not in danger of financial disaster merely because it owes itself money" ~ Andrew William Mellon
Related linux commands:
csplit - Split a file into context-determined pieces
cut - Divide a file into several parts
fmt - Reformat paragraph text
fold - Wrap input lines to fit in specified width
head - Output the first part of file(s)
paste - Merge lines of files
split - Split a file into fixed-size pieces
tail - Output the last part of files
Equivalent Windows command: FC - Compare two files