Note

Is ble.sh completely written in pure Bash?

Actually, no. The entire codebase of ble.sh is not perfectly written in pure Bash. Although the core part of the line editor is written in completely pure Bash, initialization codes, history manipulations, completion, etc. use external commands for the environment setup and efficiency. Here are the categories of the use of external commands with their reasoning.

• (init) Some initialization codes of ble.sh use external commands such as mkdir, chmod, rm, readlink, which cannot be replaced by any pure Bash functionality. Also, finalization codes use rm.

• (perf) Some computationally costly operations such as history manipulations (with many history entries) and completion (with many possible completions) use external commands such as awk, sed, and sort. In principle, it is possible to implement these processes in pure Bash script, but it is too slow. We think the user experience is more important that the fact that ble.sh is really entirely written in pure Bash script.

• (compat) There are several Bash functionalities that are not present in older Bash versions. For such functionalities, ble.sh uses external commands as fallback in old versions of Bash.

• (diag) Some codes for diagnostics (debugging ble.sh itself) use external commands.

• (user) When executing user commands which are supplied through the commandline, progcomp settings, hooks such as PROMPT_COMMAND, etc., external commands in these user commands are of course executed. In addition to this, ble.sh uses stty command to set up the correct TTY settings for these user commands. Also, when the user invoked the command help functionality, man will be executed. completion also uses man to obtain the list of available commandline options.

Here are the list of the uses of external commands in ble.sh (last updated 2020-11-11):

• (init) ble.pp: rm, mkdir, chmod, readlink
• (init) def.sh (blehook/.compatibility-ble-0.3/check): cat
• (init) util.sh (ble/util/declare-print-definitions): awk for fixing buggy output of declare -p of various versions of Bash.
• (init, perf) decode.sh (ble/decode/cmap/initialize): awk
• (init, perf) decode.sh (ble/decode/readline/.generate-source-to-unbind-default): awk
• (init, perf) decode.sh (ble/builtin/bind/read-user-settings): sed, mv, awk
• (compat <= 4.3) util.sh (ble/util/msleep): rm, mkfifo, sleep, sleepenh, usleep, etc.
• (compat <= 4.3, init) edit.sh: tty to obtain TTY name for PS1 \l
• (compat <= 4.1) util.sh (ble/util/strftime): date
• (compat <= 3.2) edit.sh: grep, rm, mkfifo to capture the user input C-d
• (user) util.sh (ble/term/stty): stty
• (user, perf) decode.sh (ble-bind -L): sed
• (user) util.sh (ble/util/pager): less, pager, more, etc. to show information to the user.
• (user) edit.sh: man, awk to show command help.
• (user) complete.sh: man, gzip, nroff, mkdir to extract and cache man information to generate completions
• (diag) util.sh (ble/debug/setdbg): rm, readlink
• (diag) benchmark.sh (ble-measure): awk to floating-point calculation
• (perf) decode.sh (ble/decode/nonblocking-read): od when there are massive user inputs
• (perf) history.sh: awk, mv, sed, wc for command history manipulations
• (perf) core-complete.sh: grep, sed, awk, sort for manipulating the list of possible completions
• (unused) util.sh (ble/util/getmtime): date, stat [Note: this function is currently not used by ble.sh itself]