Public bug reported:
When a filename contains a Unicode character outside the Basic
Multilingual Plane (specifically U+1D70B, MATHEMATICAL ITALIC SMALL PI,
`𝜋`), `ls` fails to display it correctly when writing to an SSH pty. The
character is either replaced with `????` or escaped to its octal
representation (`\360\235\234\213`), depending on the quoting style
used.
The bug does not reproduce on a local pty (tested on the same Ubuntu
26.04 machine with a display), and does not reproduce when `ls` writes
to a pipe. It is therefore specific to SSH pty output.
## Environment
- Ubuntu 26.04 (both client and server)
- ls (uutils coreutils) 0.8.0
- LANG=en_US.UTF-8
- TERM=xterm-256color
- Tested across multiple terminal emulators (xfce4-terminal, Terminator, Kitty)
— all affected identically
## Reproduction
Create a file with a SMP Unicode character in its name on a remote
machine:
`touch $'𝜋thon'`
Then from a client, compare pty vs non-pty SSH:
```
ssh -t user@remote 'ls' # broken: shows ???? or octal escape
ssh -T user@remote 'ls' # correct: shows 𝜋thon
```
Local comparison — piped vs tty:
```
ls # broken
ls | cat # correct
```
## Quoting style matrix (all styles tested, SSH pty)
All 8 supported quoting styles either escape the character to octal or
display replacement characters. No quoting style passes the raw UTF-8
bytes through correctly when writing to an SSH pty:
```
literal: ????thon
shell: ????thon
shell-always: '????thon'
shell-escape: ''$'\360\235\234\213''thon'
shell-escape-always: ''$'\360\235\234\213''thon'
locale: '\360\235\234\213thon'
clocale: "\360\235\234\213thon"
c: "\360\235\234\213thon"
```
When piped (`ls | grep thon`), `literal`, `shell`, and `shell-always`
all render `𝜋thon` correctly.
## Additional notes
- `echo '𝜋thon'` renders correctly in the same SSH session, ruling out locale
or terminal font issues
- `python3 -c "import ctypes; libc = ctypes.CDLL('libc.so.6');
libc.wcwidth.restype = ctypes.c_int; print(libc.wcwidth(0x1D70B))"` returns `1`
— glibc considers this a valid, narrow character
- GNU coreutils `ls` behaviour was not tested as it is no longer available on
Ubuntu 26.04 without manual intervention
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: coreutils 9.5-1ubuntu2+0.0.0~ubuntu25
ProcVersionSignature: Ubuntu 7.0.0-29.29-generic 7.0.12
Uname: Linux 7.0.0-29-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: XFCE
Date: Mon Aug 10 00:18:42 2026
InstallationDate: Installed on 2025-10-28 (285 days ago)
InstallationMedia: Xubuntu 24.04.1 LTS "Noble Numbat" - Release amd64 (20240827)
PackageArchitecture: all
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: coreutils-from
UpgradeStatus: Upgraded to resolute on 2026-01-22 (199 days ago)
** Affects: coreutils-from (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute
** Description changed:
When a filename contains a Unicode character outside the Basic
Multilingual Plane (specifically U+1D70B, MATHEMATICAL ITALIC SMALL PI,
`𝜋`), `ls` fails to display it correctly when writing to an SSH pty. The
character is either replaced with `????` or escaped to its octal
representation (`\360\235\234\213`), depending on the quoting style
used.
The bug does not reproduce on a local pty (tested on the same Ubuntu
26.04 machine with a display), and does not reproduce when `ls` writes
to a pipe. It is therefore specific to SSH pty output.
## Environment
- Ubuntu 26.04 (both client and server)
- - `ls (uutils coreutils) 0.8.0`
- - `LANG=en_US.UTF-8`
- - `TERM=xterm-256color`
+ - ls (uutils coreutils) 0.8.0
+ - LANG=en_US.UTF-8
+ - TERM=xterm-256color
- Tested across multiple terminal emulators (xfce4-terminal, Terminator,
Kitty) — all affected identically
## Reproduction
Create a file with a SMP Unicode character in its name on a remote
machine:
- ```bash
- touch $'𝜋thon'
- ```
+ `touch $'𝜋thon'`
Then from a client, compare pty vs non-pty SSH:
- ```bash
+ ```
ssh -t user@remote 'ls' # broken: shows ???? or octal escape
ssh -T user@remote 'ls' # correct: shows 𝜋thon
```
Local comparison — piped vs tty:
- ```bash
+ ```
ls # broken
ls | cat # correct
```
## Quoting style matrix (all styles tested, SSH pty)
All 8 supported quoting styles either escape the character to octal or
display replacement characters. No quoting style passes the raw UTF-8
bytes through correctly when writing to an SSH pty:
```
literal: ????thon
shell: ????thon
shell-always: '????thon'
shell-escape: ''$'\360\235\234\213''thon'
shell-escape-always: ''$'\360\235\234\213''thon'
locale: '\360\235\234\213thon'
clocale: "\360\235\234\213thon"
c: "\360\235\234\213thon"
```
When piped (`ls | grep thon`), `literal`, `shell`, and `shell-always`
all render `𝜋thon` correctly.
## Additional notes
- `echo '𝜋thon'` renders correctly in the same SSH session, ruling out locale
or terminal font issues
- `python3 -c "import ctypes; libc = ctypes.CDLL('libc.so.6');
libc.wcwidth.restype = ctypes.c_int; print(libc.wcwidth(0x1D70B))"` returns `1`
— glibc considers this a valid, narrow character
- GNU coreutils `ls` behaviour was not tested as it is no longer available on
Ubuntu 26.04 without manual intervention
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: coreutils 9.5-1ubuntu2+0.0.0~ubuntu25
ProcVersionSignature: Ubuntu 7.0.0-29.29-generic 7.0.12
Uname: Linux 7.0.0-29-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: XFCE
Date: Mon Aug 10 00:18:42 2026
InstallationDate: Installed on 2025-10-28 (285 days ago)
InstallationMedia: Xubuntu 24.04.1 LTS "Noble Numbat" - Release amd64
(20240827)
PackageArchitecture: all
ProcEnviron:
- LANG=en_US.UTF-8
- PATH=(custom, no user)
- SHELL=/bin/bash
- TERM=xterm-256color
- XDG_RUNTIME_DIR=<set>
+ LANG=en_US.UTF-8
+ PATH=(custom, no user)
+ SHELL=/bin/bash
+ TERM=xterm-256color
+ XDG_RUNTIME_DIR=<set>
SourcePackage: coreutils-from
UpgradeStatus: Upgraded to resolute on 2026-01-22 (199 days ago)
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https://bugs.launchpad.net/bugs/2163129
Title:
`ls` mangles Supplementary Multilingual Plane (SMP) Unicode characters
when stdout is an SSH pty
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