SAVEHIST

SAVEHIST is a configuration option in the C shell family, including csh and tcsh, that governs the persistence of command history across shell sessions. It specifies how many commands from the current session are saved to the history file when the shell exits, enabling users to recall recent commands in future sessions.

SAVEHIST is typically used alongside in-memory history settings. For example, a user might set history to keep a certain number of commands in memory during a session and also set SAVEHIST to control how many of those entries are written to disk on exit. A common pair is to set history to 1000 and savehist to 1000, though exact values and usage can vary by system and shell version.

The history file is stored in the user's home directory, with names such as ~/.history or ~/.tcsh_history being common, though the exact filename and location can differ across implementations. On startup, the shell may read the history file to populate the in-memory history, and on exit, SAVEHIST determines how many of the most recent entries are written back to the file.

Notes and limitations: The precise syntax and behavior of SAVEHIST can vary between different releases and implementations of tcsh and csh. Some systems may handle duplicates, merges, or file naming differently, and default values are system-dependent. Users often customize both in-memory history and persistent history to balance quick access to recent commands with storage considerations.

See also: tcsh, csh, history, fc, shell history management.