Re: [Haskell-cafe] how to expand ~ in a filepath

Where do you get the idea that Bash does not expand ~foo? <transcript> pc@Boole ~/Downloads $ echo $SHELL /bin/bash pc@Boole ~/Downloads $ echo ~pc /home/pc </transcript> Bash Reference Manual section 3.5.2 begins with this paragraph: <quote> If a word begins with an unquoted tilde character (‘~’), all of the characters up to the first unquoted slash (or all characters, if there is no unquoted slash) are considered a tilde-prefix. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible login name. If this login name is the null string, the tilde is replaced with the value of the HOME shell variable. If HOME is unset, the tilde expands to the home directory of the user executing the shell instead. Otherwise, the tilde-prefix is replaced with the home directory associated with the specified login name. </quote> Section 2.6.1 of the POSIX.1 shell specification describes tilde expansion, and very explicitly requires that <quote> the characters in the tilde-prefix following the <tilde> shall be treated as a possible login name from the user database </quote> so it actually *is* a standard. In fact in something like pongpath=~foo:~bar:~ugh *each* of the three tildes begins a multicharacter tilde prefix. On Wed, 23 Jul 2025 at 00:18, Mig Mit wrote:

There is no “should” here. It might be what you want, but it's not a universal standard. In Bash, “~foo” is not expanded.

Sent from my iPad

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On 2025. Jul 22., at 15:13, Richard O'Keefe wrote:

But it's not just ~/ that should be expanded. All four of "~" "~/bar" "~foo" and "~foo/bar" should be expanded by a tilde-expander.

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On Tue, 22 Jul 2025 at 03:06, Brandon Allbery wrote:

There's also https://github.com/xmonad/xmonad-contrib/blob/master/XMonad/Prelude.hs#L135-... although it also does a few other things.

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On Mon, Jul 21, 2025 at 7:57 AM Tristan Cacqueray via Haskell-Cafe wrote:

Hello, unfortunately there is no "expandHomePath" or "realpath" helpers in the standard libraries. Searching for "FilePath -> IO FilePath" in hoogle shows an implementation in the hledger project: https://hackage-content.haskell.org/package/hledger-lib-1.43.2/docs/Hledger-...

… which check if the path begins with "~/", and replace that with the output of "getHomeDirectory"

-Tristan

On Mon, Jul 21, 2025 at 07:19 PICCA Frederic-Emmanuel wrote:

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Hello, I am trying to open and read the content of this kind of filepath.

~/debian/changelog

So is there a prefered way to expand the ~ into the real $HOME.

thanks for your help

Frédéric

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-- brandon s allbery kf8nh allbery.b@gmail.com _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

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