0

So, I was playing around with this answer, when I found that neither

printf_stdin () {
    read input
    printf "$input"
}

sed "/lorem ipsum foobar/ {
   s/'/'\"'\"'/g
   s/\(lorem ipsum \)\(foobar\)/\1'\"\$(printf '%s' '\2' | printf_stdin)\"'/g
   s/.*/printf '%s' '\0'/e
}" <<< "lorem ipsum foobar"

nor

printf_ () {
    printf "$1"
}

sed "/lorem ipsum foobar/ {
   s/'/'\"'\"'/g
   s/\(lorem ipsum \)\(foobar\)/\1'\"\$(printf_ '\2')\"'/g
   s/.*/printf '%s' '\0'/e
}" <<< "lorem ipsum foobar"

works. They both output the error sh: 1: <bash function>: not found. I'm not planning to use this thing anymore, but still, I'm curious why this doesn't work and how to fix it.

Edit

Running

sed "/lorem ipsum foobar/ {
   s/'/'\"'\"'/g
   s/\(lorem ipsum \)\(foobar\)/\1'\"\$(printf '%s' '$0')\"'/g
   s/.*/printf '%s' '\0'/e
}" <<< "lorem ipsum foobar"

gives

lorem ipsum /bin/bash

so sed seems to be invoking the bash shell and not the bourne shell?

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3
  • What is your operating system? Is your /bin/sh bash or is it dash? Or something else? Commented Nov 16 at 12:58
  • If you want to do stuff combining sed, shell, function calls, etc then do yourself a favour and just use perl. It'll be easier, far more capable, faster, and you won't end up getting lost in a maze of twisty little quotation marks. Simple example: echo bar | perl -pe 'BEGIN{sub myfoo {my $str = shift; return "foo $str"}}; s/.*/myfoo $&/e' (sure, this trivial example doesn't need the /e modifier OR a function, but it does illustrate what's possible and how much easier it is than doing it in shell). people try to do too much in shell, a language that makes easy things needlessly difficult. Commented Nov 16 at 14:35
  • What is your /bin/sh? Is it perhaps a symlink to bash? Does this work if you run export -f printf_stdin before your first command? Commented Nov 17 at 16:33

2 Answers 2

Reset to default
2

sed runs shell commands in a sub-shell of the default system shell i.e. whatever /bin/sh links to (Usually a POSIX shell like dash) that shell doesn't support exporting user defined functions (which is needed in this case) i.e. printf_stdin () {...;} is defined in the current running shell (parent) and is called from a subshell (child) where that function isn't available/defined hence sh: 1: <function>: not found... That's why AFAIK.

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5
  • Hm I investigated your hypothesis, and it seems that sed runs the subshell $( ... ) as a bash shell? See the appended section titled "Edit", which I just appended. Commented Nov 16 at 8:22
  • @Grass in your edit $0 is expanded by the shell on the command line before it gets passed to sed so passed as a string ... Try something simple sed 's/.*/printf "%s\n" $0/e' <<<'blabla' instead. Commented Nov 16 at 8:31
  • Oh I see, thanks! That's pretty interesting. Would it be possible to switch to a bash shell from within the bourne shell? Commented Nov 16 at 8:34
  • @Grass I don't know if that is practically possible for sed (aside from changing the default system shell which is a bad idea and asking for trouble) ... However, making sed run Bash instead is not enough as the function defined in the parent shell needs to be exported export -f printf_stdin as the latter is the real culprit. Commented Nov 16 at 8:55
  • I see, thanks! This was interesting. Commented Nov 16 at 9:02
1

Without the shebang selecting /bin/bash, your system selects /bin/sh, an older, simpler shell, that doesn't understand the bashisms you use.

Before your file's first line,

#!/bin/bash

will tell the system to use bash, rather than sh, to interpret your script.

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2
  • Nope. My default shell is bash, plus I ran the above with a bash shebang, as you suggested, before posting my question. The same error is produced. Commented Nov 16 at 8:20
  • 2
    If you ran your script with a specific shebang then include that in the code in your question so we don't waste time diagnosing issues caused by a missing shebang. Commented Nov 16 at 15:11

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