Bulk renaming in a single pass with Go


© Lead Image © Denis Tevekov, 123RF.com

© Lead Image © Denis Tevekov, 123RF.com

Article from Issue 244/2021

Renaming multiple files following a pattern often requires small shell scripts. Mike Schilli looks to simplify this task with a Go program.

One popular interview question for system administrators is what is the easiest way to give a set of files a new extension. Take a directory of *.log files, for example: How do you rename them all in one go to *.log.old? It has reportedly happened that candidates suggested the shell command mv *.log *.log.old for this – however, they were then not hired.

There are already quite a few tools lurking around on GitHub that handle such tasks, such as the Renamer tool written in Rust [1]. But such simple utilities make for great illustrative examples, so I wanted to explore some Go techniques for bulk renaming. Paying tribute to the original, the Go variant presented below will also go by the name of Renamer. For example, to rename an entire set of logfiles ending in .log to .log.bak, just use the call shown in line 1 of Listing 1.

Or how about renaming vacation photos currently named IMG_8858.JPG through IMG_9091.JPG to hawaii-2020-0001.jpg through hawaii-2020-0234.jpg? My Go program does that too with the call from line 4, replacing the placeholder {seq} with a counter incremented by one for each renamed file, which it pads with leading zeros to four digits.


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