paste (Unix)

paste is a Unix utility that merges corresponding lines of files. It reads input lines from one or more files (or standard input if a file argument is omitted) and combines them into a single line separated by a delimiter. By default, the delimiter is a tab character.

The primary function of paste is to horizontally concatenate files. Unlike utilities like cat, which perform vertical concatenation (appending one file to the end of another), paste merges files side-by-side, line by line. This is particularly useful for combining data from different sources where each file contains a similar type of information corresponding to the same record.

paste offers options to customize its behavior. The -d option allows you to specify a different delimiter character or string to separate the joined lines. The -s option tells paste to paste all the lines from one file before proceeding to the next, essentially serializing the input instead of parallelizing it. This transforms a multi-line file into a single line.

The utility is a standard part of most Unix-like operating systems and is commonly used in shell scripts for data manipulation and report generation. It's part of the Single UNIX Specification.