tilde expansion active in quoted parameter substitution

• 回報者: mcdutchie
• 負責人: magicant
• 類型: 問題回報
• 狀態: 開啟 [Owner assigned]
• 元件: shell-main
• 里程碑: (無)
• 優先權: 3
• 嚴重程度: 5 - 中
• 處理結果: Postponed
• 檔案: 1

細節 回覆

Quoting should deactivate tilde expansion, but yash still expands tildes in quoted parameter expansions.

$ yash -c 'unset foo; echo "${foo:-~/test}"'
/Users/martijn/test

Expected output: ~/test (as per dash, bash, *ksh, zsh)

Ticket History (3/6 Histories)

2018-11-06 05:48 Updated by: mcdutchie

• New Ticket "tilde expansion active in quoted parameter substitution" created

2018-11-07 23:30 Updated by: magicant

評語 回覆

Thanks for reporting.

Looks like this is the same kind of issue as #36278. POSIX does not precisely define how double-quotes modify interpretation of other special characters.

2018-11-25 17:01 Updated by: magicant

評語 回覆

The behavior of other shells is consistent for "${unset-~}", "${unset+~}", and "${unset=~}", but for "${unset?~}"...

+ bash -o posix -c 'echo ${unset?~}'
bash: unset: /home/magicant
+ bash -o posix -c 'echo "${unset?~}"'
bash: unset: /home/magicant
+ ksh -c 'echo ${unset?~}'
ksh: unset: /home/magicant
+ ksh -c 'echo "${unset?~}"'
ksh: unset: ~
+ mksh -o posix -c 'echo ${unset?~}'
mksh: unset: /home/magicant
+ mksh -o posix -c 'echo "${unset?~}"'
mksh: unset: ~
+ zsh --emulate sh -c 'echo ${unset?~}'
zsh:1: unset: ~
+ zsh --emulate sh -c 'echo "${unset?~}"'
zsh:1: unset: ~

2018-11-25 23:23 Updated by: magicant

評語 回覆

Korn shell is quite strange in that tilde expansion is enabled in "${foo#~}" but not in "${foo##~}".

2018-11-25 23:44 Updated by: magicant

• File 0001-Don-t-tilde-expand-modifier-word-in-quoted-parameter.patch (File ID: 5438) is attached

2018-11-26 00:19 Updated by: magicant

• 優先權 Update from 5 - 中 to 3
• 元件 Update from (無) to shell-main
• 處理結果 Update from 無 to Postponed
• 負責人 Update from (無) to magicant

評語 回覆

The attached patch should fix this.

On second thought, however, I'm in doubt whether this should be really "fixed." POSIX explicitly says, "In each case that a value of word is needed (based on the state of parameter, ...), word shall be subjected to tilde expansion, parameter expansion, command substitution, and arithmetic expansion." (XCU 2.6.2) POSIX does not explicitly require tilde expansion be disabled in quoted expansion. Then what interpretation of POSIX can deny the current behavior of yash?

I'm postponing this, maybe until POSIX is revised for clarity.