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by 1vuio0pswjnm7
1512 days ago
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This is useful when saving command lines to files (scripts) using the POSIX-required fc builtin. Command line histories are relatively cumbersome to save with Ash, Bash saves them but truncates them to 500 entries, whereas scripts can easily be saved indefinitely. Amongst Bash and other feature-heavy shell users, there are Rube Goldberg-like workarounds for command line history saving. OTOH, all shells aiming for POSIX compliance, including the fastest, lightest weight ones I prefer, will implement fc. It's already there; I make use of it. I will type fc, save to a file (script) and then delete all lines before exiting the default EDITOR, e.g., %d in vi. This prevents the commands from being re-executed when I exit vi. Also I sometimes use # combined with a semicolon to disable portions of command lines, e.g., early commands ;# late commands. I might cut and paste from one entry in the history into another one. Or I might fc -l 1 > file and edit the file down the the entries that form the starting point for a new script. By far, the shell is the most useful REPL for me. There is no shortage of comments online praising the utility of the REPL concept but the only comment I have ever seen about fc was from a shell implementor/maintainer; it was negative. I use fc all the time. It has become essential for me to use the shell effectively as a REPL. |
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That behavior can be modified with the HISTSIZE environment variable.
> The maximum number of commands to remember on the history list. If the value is 0, commands are not saved in the history list. Numeric values less than zero result in every command being saved on the history list (there is no limit). The shell sets the default value to 500 after reading any startup files.
https://www.gnu.org/software/bash/manual/html_node/Bash-Vari...