Thanks for the explanation and the help! On Mon, Jan 16, 2023 at 1:53 PM Chet Ramey <chet.ra...@case.edu> wrote:
> On 1/16/23 12:36 PM, dave.dram...@gmail.com wrote: > > Configuration Information [Automatically generated, do not change]: > > Machine: x86_64 > > OS: linux-gnu > > Compiler: gcc > > Compilation CFLAGS: -g -O2 -flto=auto -ffat-lto-objects -flto=auto > -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security > -Wall > > uname output: Linux sulfur 5.15.0-58-generic #64-Ubuntu SMP Thu Jan 5 > 11:43:13 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux > > Machine Type: x86_64-pc-linux-gnu > > > > Bash Version: 5.1 > > Patch Level: 16 > > Release Status: release > > > > Description: > > > > I have `set -x` and `BASH_XTRACEFD=1` set in a simple script that > I have in > > a cron job. I'd like to see the progress of the script when run > manually, > > hence `set -x`, but I want the output to go to stdout rather than > stderr so > > that cron emails me only when there is an actual failure. With this > > configuration, the `read` command is erroneously reading the "+" > prompt > > output from `set -x` into the variable. It seems like stdout is > not getting > > flushed propertly. > > > > Repeat-By: > > The following script attempts to read the first column of data, > line by > > line, into a variable called `$var`. With `BASH_XTRACEFD` unset, it > > propertly prints r1c1, r2c1, r3c1, r4c1. With `BASH_XTRACEFD=1`, > `$var` > > gets set to +, ++, r2c1, r3c1, r4c1. Maybe I am just being dumb? > > > > ``` > > #!/usr/bin/env bash > > > > BASH_XTRACEFD=1 > > set -x > > > > data=$(cat << END > > r1c1 r1c2 r1c3\n > > r2c1 r2c2 r2c3\n > > r3c1 r3c2 r3c3\n > > r4c1 r4c2 r4c3 > > END > > ) > > > > echo -e $data | while read -r var junk; do > > echo "var = $var" > > done > > ``` > > As you discovered, BASH_XTRACEFD makes the xtrace output write to the > designated file descriptor. If you write to fd 1, you're going to write the > trace output into the pipe, where `read' will see it. > > -- > ``The lyf so short, the craft so long to lerne.'' - Chaucer > ``Ars longa, vita brevis'' - Hippocrates > Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/ > >
