显示当前变量IFS
:
echo $IFS |xxd
00000000: 0a
我想将 IFS
重置为默认值 \t\n
。
IFS=$' \t\n'
echo $IFS |xxd
00000000: 0a
为什么不能重置 IFS 变量?
最佳答案
您正在重置 IFS
正确。问题出在你的echo
.你应该使用 echo -n "$IFS" | xxd
.
看看man bash
(强调我的):
Word Splitting
The shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not occur within double quotes for word splitting.
The shell treats each character of
IFS
as a delimiter, and splits the results of the other expansions into words on these characters. IfIFS
is unset, or its value is exactly<space><tab><newline>
, the default, then sequences of<space>
,<tab>
, and<newline>
at the beginning and end of the results of the previous expansions are ignored, and any sequence ofIFS
characters not at the beginning or end serves to delimit words. IfIFS
has a value other than the default, then sequences of the whitespace charactersspace
andtab
are ignored at the beginning and end of the word, as long as the whitespace character is in the value ofIFS
(anIFS
whitespace character). Any character inIFS
that is notIFS
whitespace, along with any adjacentIFS
whitespace characters, delimits a field. A sequence ofIFS
whitespace characters is also treated as a delimiter. If the value ofIFS
is null, no word splitting occurs.
因为你没有双引号 IFS
,它通过 shell 的分词逻辑。自 IFS
根据定义包含 IFS
自身内部的字符,它们会被 shell 忽略。双引号可以防止这种情况。
关于reset - 为什么不能重置 IFS 变量?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62470380/