PS1 command substitution fails when containing newlines on msys bash
This command succeeds
$ PS1='$(date +%s) $ ' 1391380852 $
However if I add a newline it fails
$ PS1='$(date +%s)\n$ ' bash: command substitution: line 1: syntax error near unexpected token `)' bash: command substitution: line 1: `date +%s)'
If I use backticks it works
$ PS1='`date +%s`\n$ ' 1391381008 $
but backticks are discouraged. So what is causing this error?
GNU bash, version 4.2.45(6)-release
You can disambiguate the parsing easily, to prevent hitting any such bug (though I can't reproduce it myself):
PS1='$(date +%s)'$'\n$ '
This $'\n' syntax parses to a literal newline character, whereas '\n' parses to a string containing a two-character \n escape sequence.
For more info on how $'' differs from '' (expanding backslash-escaped sequences) refer to the Bash Hackers Wiki.
I had a similar issue with .git-prompt when I tried to include it in my PS1 on bash (MSYS2) on Windows. The problem is the \n, if I remove it everything run smoothly but I want to break-line.
By the way on Linux everything is working fine.
The bash is run is: 4.3.42(5)-release (x86_64-pc-msys)
Old, problematic PS1:
PS1='\e[32m\]\u@\h \e[36m\]\w \e[32m\]$(__git_ps1 "(%s)")\nλ \e[0m\]$(tput sgr0)'
PS1='\e[32m\]\u@\h \e[36m\]\w \e[32m\]$(__git_ps1 "(%s)")'$'\nλ \e[0m\]'
Simplified version (no colors, copy-paste-edit it):
PS1='\u@\h \w $(__git_ps1 "(%s)")'$'\n$ '
Cheers Charles Duffy finding the problem!