Bash PS1 Generator

The variable defining the bash prompt takes a collection of backslash escapes: user, host, directory, time, the symbol that changes depending on whether you are root. Memorising that does not pay off — there are more than twenty codes and nobody touches their prompt often enough to retain them.

Pick the elements and the colours and the page assembles the variable. The technical detail causing the most trouble shows up right there: colour sequences must sit between the non-printing start and end markers. Without them, bash counts the invisible colour characters in the prompt length, and the result is the command line overwriting itself when you scroll history or edit a long command.

To apply permanently, the definition goes in the file read by interactive shells, typically ~/.bashrc. Worth remembering that there is also the continuation prompt variable, the one appearing when a command is incomplete, and the trace one used when script debugging is enabled — if you have ever got lost in a script with many repeated lines, configuring that last one with the line number helps a great deal.