paste

Merge lines of files side by side

low risk

interactive breakdown — edit the command and press Explain
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What it does

Joins corresponding lines of files using a delimiter (default tab).

Common flags
FlagMeaning
-dDelimiter
-sSerial: join all lines of one file
Examples
paste -sd, file.txtJoin lines with commas · explain & risk-check →
paste a.txt b.txtTwo columns · explain & risk-check →
Related
join cut
Open the full explainer →More in Text Processing

Reference text is hand-written and may be incomplete — check man paste for your version. Test destructive commands on a non-production system first.