How to Get File Size in Bytes on Linux and macOS

Published Jul 6, 2022

How can we get a file size in bytes on Linux and macOS?

Suppose we want the file size of file.log.

1. Using stat

stat -c %s file.log       # GNU/Linux
stat --format=%s file.log # GNU/Linux
stat -f %z file.log       # BSD/macOS

The stat utility executes the lstat syscall to obtain the file length. It does not read the file, so performance of this command does not depend on the file size.

2. Using ls

We can use ls with the -l flag to view the file metadata in the long list format.

Using -h will append the unit suffix to the file size in bytes: B, K, M, G, T and P.

ls -lh file.log

We can also use awk to print just the file size in bytes.

ls -lh file.log | awk '{print  $5}'

Similar to stat, the ls utility executes the lstat syscall to obtain the file length. It does not read the file, so performance of this command does not depend on the file size.

3. Using wc

Using wc requires reading through the entire file stream to count the bytes. While being a clean option, it isn’t the best option in regards to speed and resource usage.

It also does not work without read access to the file.

wc -c file.log   # Outputs size + filename
wc -c < file.log # Outputs size