shell下字符的匹配问题
Shell环境下如何匹配tab也就是空白分隔符呢？在man bash中我们找到这么一段话
Words of the form $'string' are treated specially.The word expands to
string, with backslash-escaped characters replaced as specified bythe ANSICstandard.Backslash escape sequences, if present, are decoded as follows:
\a alert (bell)
\b backspace
\e an escape character
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\\ backslash
\' single quote
\nnn the eight-bit character whose value istheoctalvalue
nnn (one to three digits)
\xHH theeight-bitcharacterwhose value is the hexadecimal
value HH (one or two hex digits)
\cx a control-x character
The expanded result is single-quoted, as if thedollarsignhadnot been present.
也就是说在shell环境下可以使用\t的转义序列，需要在前面加上$符号，让bash本身分开来识别。
问题：我们如何通过48和后面的一个tab来过滤出第一行呢？
# cat temp
48 Mike
480 Ken
48
方法一：
# grep $'48\t' temp
48 Mike
方法二：
# grep '48' temp
48 Mike
方法三:
# grep -P '48\t' temp
48 Mike
-P, --perl-regexp
Interpret PATTERN as a Perl regular expression.
方法四：
# grep '48[[:space:]]' temp
48 Mike
方法五：
# sed -n '/48\t/p' temp
48 Mike
方法六：
# awk '/48\t/' temp
48 Mike
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