windowBed searches for overlapping features in A and B. However, windowBed adds a specified number (1000, by default) of base pairs upstream and downstream of each feature in A. In effect, this allows features in B that are near features in A to be detected.
Parent program: BEDTools
bedtools utilities are a swiss-army knife of tools for a wide-range of genomics analysis tasks. The most widely-used tools enable genome arithmetic: that is, set theory on the genome. For example, bedtools allows one to intersect, merge, count, complement, and shuffle genomic intervals from multiple files in widely-used genomic file formats such as BAM, BED, GFF, GTF, VCF. While each individual tool is designed to do a relatively simple task (e.g., intersect two interval files), quite sophisticated analyses can be conducted by combining multiple bedtools operations on the UNIX command line.