You forgot to Cc: the mailing list. I think this was on bug-bash...? On Fri, Mar 16, 2018 at 02:06:09PM -0400, Boruch Baum wrote: > On 2018-03-16 09:22, Greg Wooledge wrote: > > On Fri, Mar 16, 2018 at 09:14:13AM -0400, Boruch Baum wrote: > > > In GNU bash, version 4.4.18(1)-release (x86_64-pc-linux-gnu), the first > > > line of the documentation for readarray / mapfile states: > > > > > > Read lines from the standard input ... > > > > > > However, it doesn't seem to accept input from a pipe. It would be > > > helpful to note that. > > > > It does. What you're running into is the fact that each component of > > the pipeline is run in a separate subshell, so any variables assignments > > made during the pipeline (including read or mapfile) are lost once the > > pipeline is completed. > > > > https://mywiki.wooledge.org/BashFAQ/024 > > I'm afraid what prompted me to file the report was something more > subtle. Upon trying my test one-liner on a second virtual terminal, the > one-liner worked, so I'm now trying to figure out what settings might > affect the behavior. My test one-liner is: > > printf "aa bb\n cc\n" | readarray ; echo ${MAPFILE[0]}
First: https://mywiki.wooledge.org/Quotes Second: how are you defining "Fail" and "Success"? What result did you get? What result did you expect? What was in this variable before you ran your tests? > Comparing the two bash instances: > > FAIL SUCCESS > lastpipe off off (Note that lastpipe only works if job control is disabled.) > I considered maybe IFS was set wrong, but that's not it > > echo $IFS |xxd > 00000000: 0a That is the single most spectacularly useless command I've seen in quite a while. A wonderful teaching example! I should put it in a quiz. "What does this command print? Why? Why doesn't it matter what the actual value of IFS is?" Again: https://mywiki.wooledge.org/Quotes This command will never reveal any information, period. Every character of IFS is guaranteed to be eaten by IFS splitting since you failed to quote. That's why echo receives no arguments, and only writes a single newline to stdout. Try this one instead: printf %s "$IFS" | xxd Or better still: printf %s "$IFS" | od -An -tx1 IFS will definitely affect the result of your unquoted MAPFILE expansion. So don't use an unquoted ${MAPFILE[@]} either. Quote properly. Always. > I then tried explicitly setting the delimiter using -d"\n", -d'\n' and > -d\n, to no avail. (What command did you run? What output did you get? What output did you expect?) > I've also tried changing the echo statement to "echo $? ${MAPfile[0]}", > which returns just the zero. https://mywiki.wooledge.org/Quotes Also you misspelled MAPFILE. > type mapfile > mapfile is a shell builtin > > which mapfile ; echo $? > 1 And now you know why you don't use which(1) for this. > Any ideas? Quote properly. Show your actual results, and how you got them. State your expected results. wooledg:~$ echo hello world | (readarray; declare -p MAPFILE) declare -a MAPFILE=([0]=$'hello world\n') wooledg:~$ echo hello world | readarray wooledg:~$ declare -p MAPFILE bash: declare: MAPFILE: not found wooledg:~$ shopt -s lastpipe wooledg:~$ echo hello world | readarray; declare -p MAPFILE bash: declare: MAPFILE: not found wooledg:~$ set +m wooledg:~$ echo hello world | readarray; declare -p MAPFILE declare -a MAPFILE=([0]=$'hello world\n') lastpipe will typically work in a script, because job control (set +m) is disabled in scripts by default. The reverse is true in an interactive shell.
