如果你能帮助我弄清楚如何确定变量的内容是否以井号开头,我将感激不尽:
#!bin/sh myvar="#comment asfasfasdf" if [ myvar = #* ]
这不起作用.
谢谢!
JANS
解决方法@H_502_12@
一种方法是使用“子串扩展”来切掉变量内容的第一个字符:
if [[ ${x:0:1} == '#' ]]
then
echo 'yep'
else
echo 'nope'
fi
yep
从Bash手册页:
${parameter:offset}
${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 start-
ing at the character specified by offset. length and offset are
arithmetic expressions (see ARITHMETIC EVALUATION below).
length must evaluate to a number greater than or equal to zero.
If offset evaluates to a number less than zero,the value is
used as an offset from the end of the value of parameter. If
parameter is @,the result is length positional parameters
beginning at offset. If parameter is an array name indexed by @
or *,the result is the length members of the array beginning
with ${parameter[offset]}. A negative offset is taken relative
to one greater than the maximum index of the specified array.
Note that a negative offset must be separated from the colon by
at least one space to avoid being confused with the :- expan-
sion. Substring indexing is zero-based unless the positional
parameters are used,in which case the indexing starts at 1.
编辑:
当然,如果您转义哈希,您的原始方法会正常工作:
$[[ '#snort' == \#* ]]; echo $?
0
if [[ ${x:0:1} == '#' ]] then echo 'yep' else echo 'nope' fi yep
从Bash手册页:
${parameter:offset} ${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 start- ing at the character specified by offset. length and offset are arithmetic expressions (see ARITHMETIC EVALUATION below). length must evaluate to a number greater than or equal to zero. If offset evaluates to a number less than zero,the value is used as an offset from the end of the value of parameter. If parameter is @,the result is length positional parameters beginning at offset. If parameter is an array name indexed by @ or *,the result is the length members of the array beginning with ${parameter[offset]}. A negative offset is taken relative to one greater than the maximum index of the specified array. Note that a negative offset must be separated from the colon by at least one space to avoid being confused with the :- expan- sion. Substring indexing is zero-based unless the positional parameters are used,in which case the indexing starts at 1.
编辑:
当然,如果您转义哈希,您的原始方法会正常工作:
$[[ '#snort' == \#* ]]; echo $? 0