On Sun, Feb 13, 2022, 22:23 <vzvz...@gmail.com> wrote: > Configuration Information [Automatically generated, do not change]: > Machine: x86_64 > OS: linux-gnu > Compiler: gcc > Compilation CFLAGS: -g -O2 > -fdebug-prefix-map=/build/bash-a6qmCk/bash-5.0=. -fstack-protector-strong > -Wformat -Werror=format-security -Wall -Wno-parentheses -Wno-format-security > uname output: Linux zoli-linux 5.13.0-28-generic #31~20.04.1-Ubuntu SMP > Wed Jan 19 14:08:10 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux > Machine Type: x86_64-pc-linux-gnu > > Bash Version: 5.0 > Patch Level: 17 > Release Status: release > > Description: > > Background > ---------- > > Commit a0c0a00fc419b7bc08202a79134fcd5bc0427071 (bash-4.4) introduced a > change in parse.y with following documentation in the change logs: > > parse.y > - shell_getc: if bash is reading input from a string that ends > with an > unquoted backslash, add another backslash instead of a newline, > since > the backslash and newline will disappear in normal processing. > Fixes > bug with `bash -c 'eval \\; echo y' ' skipping the eval command > and > setting incorrect exit status, and `bash -ic 'eval \\; echo y' ' > seeing EOF on empty line and exiting before the echo. Keep > track of > backslash state with last_was_backslash; set in char reading > loop. > Fixes bug reported by Eduardo A. Bustamante López < > dual...@gmail.com> > > The new code in parse.y > > /* Don't add a newline to a string that ends with a backslash if > we're > going to be removing quoted newlines, since that will eat the > backslash. Add another backslash instead (will be removed by > word expansion). */ > if (bash_input.type == st_string && expanding_alias() == 0 && > last_was_backslash && c == EOF && remove_quoted_newline) > shell_input_line[shell_input_line_len] = '\\'; > else > shell_input_line[shell_input_line_len] = '\n'; > shell_input_line[shell_input_line_len + 1] = '\0'; > > > This specific change is also there in commit > 0385211bb5cb01e0259c64ec2c5cc6337d4e215c on a development branch. > > Observed vs. expected behaviour > ------------------------------- > > The mentioned bug is indeed fixed by this change. However, in case of > another edge case following new behaviour is observable: > > $ bash -c 'echo \' > \ > $ # backslash appears on output >
bash -c recognized a backslash due to smarter input checking as arg instead of newline break The behaviour before the change was following: > > $ bash -c 'echo \' > > $ # no output > bash -c recognized \ \n eof do you know, $' foo \' bar \' ' to preseeve 's if u dont This behaviour is observable since 4.4 up to the most current released > version (5.1). > > I am not sure what is the correct behaviour here. My best guess is, that > the single backslash at the end of the string should not be printed, > because (bash man page): > > Quote Removal > After the preceding expansions, all unquoted occurrences of the > characters \, ', and " that did not result > from one of the above expansions are removed. > > This behaviour would be consistent with the very same command took from a > script: > > $ hexdump -C echo-with-newline.sh > 00000000 65 63 68 6f 20 5c 0a |echo \.| > 00000007 > $ hexdump -C echo-without-newline.sh > 00000000 65 63 68 6f 20 5c |echo \| > 00000006 > $ bash echo-with-newline.sh > > $ bash echo-without-newline.sh > > $ # no output in both cases > > Repeat-By: > See commands in the description. > > >
