How to set the last command exit code in Bash?
You need to call the function within a command substitution, e.g. $ (exit_status), or from PROMPT_COMMAND. If you do, take care with the \\ [ .. \\] escapes: Bash interprets them before other expansions in the prompt, so you have to hardcode them in the prompt string (they can’t be parts of variables or other things expanded in the prompt).
Do you have to hardcode the bash prompt escapes?
If you do, take care with the \\ [ .. \\] escapes: Bash interprets them before other expansions in the prompt, so you have to hardcode them in the prompt string (they can’t be parts of variables or other things expanded in the prompt). And if not expanding the prompt escapes from variables seems backwards to you, I can’t blame you.
How to save the exit code of a command substitution?
If call the function with a command substitution from inside the prompt string, then you need a workaround, as the exit code of the command substitution takes effect. Something like this: I would use the version with PROMPT_COMMAND, just to save the subshell fork caused by the command substitution, but in practice the effect is minimal.
How to expand the value of a command in Bash?
Bash has a fairly consistent syntax with regards to value expansions: they all start with a $ symbol. Command Substitution essentially expands the value of a command that was executed in a subshell. As such, the syntax is a combination of the value-expansion prefix $ followed by the subshell to expand: (…).
How to display the last command in Linux?
-R: This option is used to hide the host-name field. -F: This option is used to display the login and logout time including the dates. -a: This option is used is to display the host-name in the last column. -s, -t: This option is used to display within a specific time period.
How to use Bash history commands and expansions?
The typical way of utilizing this is through searching backwards in history (most recent results returned first) using the CTRL-r key combination. For instance, you can type CTRL-r, and begin typing part of the previous command. You only have to type out part of the command.