Package: dash Version: 0.5.8-2.4 Severity: normal Tags: upstream X-Debbugs-CC: Michael Prokop <[email protected]>
Hi! While tracking an issue with some scripts (described at [I]) we noticed that dash is not POSIX compliant when parsing the script to invoke from stdin. In contradiction with POSIX, it does block reads instead of character-per-character reads to only get the current command, quoting from POSIX [P]: ,--- | STDIN | | […] | | When the shell is using standard input and it invokes a command that | also uses standard input, the shell shall ensure that the standard | input file pointer points directly after the command it has read | when the command begins execution. It shall not read ahead in such a | manner that any characters intended to be read by the invoked | command are consumed by the shell (whether interpreted by the shell | or not) or that characters that are not read by the invoked command | are not seen by the shell. When the command expecting to read | standard input is started asynchronously by an interactive shell, it | is unspecified whether characters are read by the command or | interpreted by the shell. `--- [I] <https://michael-prokop.at/blog/2017/05/18/debugging-a-mystery-ssh-causing-strange-exit-codes/> [P] <http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sh.html> The following test demonstrates the problem: ,--- sh-stdin.sh --- #!/bin/sh : ${TEST_SH:=dash} $TEST_SH <<"EOF" echo "Inner: pre" while read line; do echo "Eat: $line"; done echo "Inner: post" exit 3 EOF echo "Outer: exit code = $?" `--- ,--- test session --- $ TEST_SH=bash ./sh-stdin Inner: pre Eat: echo "Inner: post" Eat: exit 3 Outer: exit code = 0 $ TEST_SH=dash ./stdin.sh Inner: pre Inner: post Outer: exit code = 3 `--- All other shells that we tested are POSIX compliant, this includes: bash, ksh, mksh, posh and zsh Thanks, Guillem
