Master Linux File Splitting and Merging with split and cat Commands

File Splitting with split

Linux provides the split utility to break a large file into smaller pieces that can be transferred independently and later reassembled.

Syntax

split [OPTIONS] [INPUT_FILE] [PREFIX]

Key options

-a N

– suffix length (default 2, produces aa, ab …) -d – use numeric suffixes starting at 0 -l LINES – split after each LINES lines (default 1000) -b SIZE – split by byte size; SIZE may use K, M, G, … (powers of 1024) or KB, MB … (powers of 1000) -C SIZE – split by byte size while preserving whole lines (no line is broken) --additional-suffix=SUF – append an extra suffix to each output name --elide-empty-files – do not create empty output files --filter=CMD – pipe each chunk to CMD instead of writing a file --verbose – print progress information

Typical usage

# Split a 300 000‑line SQL dump into 300 000‑line chunks
split -l 300000 users.sql /data/users_

# Same, but numeric suffixes (users_00, users_01 …)
split -d -l 300000 users.sql /data/users_

# Split by size, 100 MiB per file, numeric suffixes
split -d -b 100m users.sql /data/users_

Notes on size units

SIZE may be an integer followed by an optional unit. Units K, M, G, T, P, E, Z, Y represent powers of 1024; the suffixes KB, MB, … represent powers of 1000. Example: 100m = 100 MiB (100 × 1024 × 1024 bytes).

File Merging with cat

After splitting, the cat command concatenates the pieces back into the original file.

Syntax

cat [OPTIONS] [FILE]...

Common options

-n

– number all output lines -e – display $ at end of each line -t – display TAB characters as

^I

Reassembly example

# Reassemble the split files into the original dump
cat /data/users_* > users.sql

Important considerations

Use a glob pattern that matches the split files in the correct lexical order; numeric suffixes guarantee proper ordering (e.g., users_00, users_01).

If the split was performed with -C (line‑preserving), the reassembled file will be byte‑identical to the original.

Both utilities belong to GNU coreutils; documentation is available at http://www.gnu.org/software/coreutils/.