bash 如何在bash中检查字符串中的最后一个字符？
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How can I check the last character in a string in bash?
提问by Mild Fuzz
I need to ensure that the last character in a string is a /
我需要确保字符串中的最后一个字符是 /
x="test.com/"
if [[ $x =~ //$/ ]] ; then
x=$x"extention"
else
x=$x"/extention"
fi
at the moment, false always fires.
目前， false 总是会触发。
回答by fedorqui 'SO stop harming'
Like this, for example:
像这样，例如：
$ x="test.com/"
$ [[ "$x" == */ ]] && echo "yes"
yes
$ x="test.com"
$ [[ "$x" == */ ]] && echo "yes"
$
$ x="test.c/om"
$ [[ "$x" == */ ]] && echo "yes"
$
$ x="test.c/om/"
$ [[ "$x" == */ ]] && echo "yes"
yes
$ x="test.c//om/"
$ [[ "$x" == */ ]] && echo "yes"
yes
回答by devnull
Your condition was slightlyincorrect. When using =~, the rhs is considered a pattern, so you'd say patternand not /pattern/.
你的情况有点不正确。使用时=~，rhs 被视为一种模式，因此您会说pattern而不是/pattern/。
You'd have got expected results if you said
如果你说，你会得到预期的结果
if [[ $x =~ /$ ]] ; then
instead of
代替
if [[ $x =~ //$/ ]] ; then
回答by devnull
You can index strings in Bash using ${var:index}and ${#var}to get the length of the string. Negative indices means the moving from the end to the start of the string so that -1is index of the last character:
您可以在 Bash 中使用${var:index}和索引字符串${#var}以获取字符串的长度。负索引意味着从字符串的末尾移动到开头，因此-1是最后一个字符的索引：
if [[ "${x:${#x}-1}" == "/" ]]; then
# last character of x is /
fi
回答by crafter
You can do this generically using bash substrings $(string:offset:length}- lengthis optional
您可以使用 bash 子字符串一般地执行此操作$(string:offset:length}-length是可选的
#xis the length of x
#x是 x 的长度
Therefore
所以
$n = 1 # 1 character
last_char = ${x:${#x} - $n}
For future references,
供以后参考，
$ man bash
has all the magic
拥有所有的魔力
${parameter:offset:length}
Substring Expansion. Expands to up to length characters of parameter starting at the character specified by offset. If length is omitted, expands to the substring of parameter starting at the character specified by offset. length and offset are arithmetic expressions ...
${参数：偏移：长度}
子串扩展。从 offset 指定的字符开始，最多扩展到参数的 length 个字符。如果省略length，则扩展到从offset 指定的字符开始的参数的子字符串。长度和偏移量是算术表达式...
