3 ms·

OK interesting, I knew about the -e -n flags issue, which means that any portable shell script has to use printf, not echo. Didn't quite realize that the use o

by chubot 3mo ago

OK interesting, I knew about the -e -n flags issue, which means that any portable shell script has to use printf, not echo. Didn't quite realize that the use of backslash also forces printf ... what a mess

gaigalas 3mo ago
Here's how I deal with it using feature detection: case "$({ printf %b "\\061" || print -r -- 2 || echo -n -e "\\063" || command -p printf %b "\\064"; } 2>/dev/null)" in 1) alias _printb1='printf %b' alias _printn1='printf %s' ;; 2) alias _printb1='print -n --' alias _printn1='print -nr --' ;; 3) alias _printb1='echo -n -e' alias _printn1='echo -n -E' ;; 4) _printb1 () { command -p printf '%b' "$1"; } _printn1 () { command -p printf '%s' "$1"; } ;; '-e 3') _pdash () { _pd=$1; while :; do case $_pd in -*) echo -n "\\055"; _pd=${_pd#-};; *) break;; esac; done; } _printb1 () { _pdash "$1"; echo -n "$_pd"; } _printn1 () { local _p _r _pdash "$1"; _r=$_pd while case $_r in *"$_BS"*) :;; *) false;; esac; do _p=${_r%%"$_BS"*} _r=${_r#*"$_BS"} echo -n "$_p$_BS$_BS" done _pdash "$_r"; _r=$_pd echo -n "$_r" } ;; *) exit 1;; esac 1) is for shells who have printf, 2) is for the ksh family, 4) is for PATH='' yash exclusively, -e 3) is for posh exclusively. It exports two callables, _printb1 and _printf1 that escape and don't escape backslashes respectively, are immune to trailing dash gotchas and other pitfalls. Unfortunatelly, not all shells allow overriding `echo` so I can't proper polyfill when necessary. I'm going to extremes here, but a simpler version of this can be used for the most popular shells.
- chubot 3mo ago
  I think that is basically the approach modernish uses: https://github.com/modernish/modernish https://github.com/modernish/modernish But it does feel complex to me. Personally I just write in the common subset of bash and OSH, which is very large. I never need to support say dash, since every machine that has dash also has bash, which is less broken in terms of 'echo' and so forth. bash has its own broken-ness, but running under OSH solves that. And OSH also supports some busybox idioms -- we learned last year that bash cannot run busybox ash scripts on Alpine e.g. 'chdir' is an alias for 'cd' in busybox, but not in bash. And Alpine scripts use it, so bash can't run Alpine scripts, but OSH can (as of last year).
  - gaigalas 3mo ago
    One of the reasons for using dash is speed. It's so fast, it allows people to write programs that were not viable before. The pure shell C compiler is an example of that: https://gist.github.com/alganet/2b89c4368f8d23d033961d8a3deb5c19 https://gist.github.com/alganet/2b89c4368f8d23d033961d8a3deb... It's portable among the most popular shells, but much faster on dash. It's obviously a gimmick, but also a way to stress the interpreters past their usual breaking points. osh fails at it because of multi-command/block-level alias (I opened an issue with a simplified reproduction). --- Options are good. Shell is amazing at that, lots of interpreters to serve all kinds of users and use cases.

by chubot 3mo ago

gaigalas 3mo ago

Here's how I deal with it using feature detection: case "$({ printf %b "\\061" || print -r -- 2 || echo -n -e "\\063" || command -p printf %b "\\064"; } 2>/dev/null)" in 1) alias _printb1='printf %b' alias _printn1='printf %s' ;; 2) alias _printb1='print -n --' alias _printn1='print -nr --' ;; 3) alias _printb1='echo -n -e' alias _printn1='echo -n -E' ;; 4) _printb1 () { command -p printf '%b' "$1"; } _printn1 () { command -p printf '%s' "$1"; } ;; '-e 3') _pdash () { _pd=$1; while :; do case $_pd in -*) echo -n "\\055"; _pd=${_pd#-};; *) break;; esac; done; } _printb1 () { _pdash "$1"; echo -n "$_pd"; } _printn1 () { local _p _r _pdash "$1"; _r=$_pd while case $_r in *"$_BS"*) :;; *) false;; esac; do _p=${_r%%"$_BS"*} _r=${_r#*"$_BS"} echo -n "$_p$_BS$_BS" done _pdash "$_r"; _r=$_pd echo -n "$_r" } ;; *) exit 1;; esac 1) is for shells who have printf, 2) is for the ksh family, 4) is for PATH='' yash exclusively, -e 3) is for posh exclusively. It exports two callables, _printb1 and _printf1 that escape and don't escape backslashes respectively, are immune to trailing dash gotchas and other pitfalls. Unfortunatelly, not all shells allow overriding `echo` so I can't proper polyfill when necessary. I'm going to extremes here, but a simpler version of this can be used for the most popular shells.

chubot 3mo ago
I think that is basically the approach modernish uses: https://github.com/modernish/modernish https://github.com/modernish/modernish But it does feel complex to me. Personally I just write in the common subset of bash and OSH, which is very large. I never need to support say dash, since every machine that has dash also has bash, which is less broken in terms of 'echo' and so forth. bash has its own broken-ness, but running under OSH solves that. And OSH also supports some busybox idioms -- we learned last year that bash cannot run busybox ash scripts on Alpine e.g. 'chdir' is an alias for 'cd' in busybox, but not in bash. And Alpine scripts use it, so bash can't run Alpine scripts, but OSH can (as of last year).
- gaigalas 3mo ago
  One of the reasons for using dash is speed. It's so fast, it allows people to write programs that were not viable before. The pure shell C compiler is an example of that: https://gist.github.com/alganet/2b89c4368f8d23d033961d8a3deb5c19 https://gist.github.com/alganet/2b89c4368f8d23d033961d8a3deb... It's portable among the most popular shells, but much faster on dash. It's obviously a gimmick, but also a way to stress the interpreters past their usual breaking points. osh fails at it because of multi-command/block-level alias (I opened an issue with a simplified reproduction). --- Options are good. Shell is amazing at that, lots of interpreters to serve all kinds of users and use cases.