试图从 bash 错误中的字符串中检索前 5 个字符？
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Trying to retrieve first 5 characters from string in bash error?
提问by Mo.
I'm trying to retrieve the first 5 characters from a string and but keep getting a Bad substitutionerror for the string manipulation line, I have the following lines in my teststring.shscript:
我正在尝试从字符串中检索前 5 个字符，但不断收到Bad substitution字符串操作行的错误，我的teststring.sh脚本中有以下几行：
TESTSTRINGONE="MOTEST"
NEWTESTSTRING=${TESTSTRINGONE:0:5}
echo ${NEWTESTSTRING}
I have went over the syntax many times and cant see what im doing wrong
我已经多次检查语法，但看不出我做错了什么
Thanks
谢谢
回答by Alex L
Depending on your shell, you may be able to use the following syntax:
根据您的 shell，您可以使用以下语法：
expr substr $string $position $length
So for your example:
所以对于你的例子：
TESTSTRINGONE="MOTEST"
echo `expr substr ${TESTSTRINGONE} 0 5`
Alternatively,
或者，
echo 'MOTEST' | cut -c1-5
or
或者
echo 'MOTEST' | awk '{print substr($ TESTSTRINGONE="MOTEST"
$ NEWTESTSTRING=${TESTSTRINGONE:0:5}
$ echo ${NEWTESTSTRING}
MOTES
,0,5)}'
回答by Balaswamy Vaddeman
echo 'mystring' |cut -c1-5is an alternative solution to ur problem.
echo 'mystring' |cut -c1-5是您问题的替代解决方案。
more on unix cut program
更多关于unix cut 程序
回答by Balaswamy Vaddeman
Works here:
在这里工作：
printf "%.5s" $TESTSTRINGONE
What shell are you using?
你用的是什么壳？
回答by Gordon Davisson
Substrings with ${variablename:0:5}are a bash feature, not available in basic shells. Are you sure you're running this under bash? Check the shebang line (at the beginning of the script), and make sure it's #!/bin/bash, not #!/bin/sh. And make sure you don't run it with the shcommand (i.e. sh scriptname), since that overrides the shebang.
子字符串${variablename:0:5}是 bash 功能，在基本 shell 中不可用。你确定你是在 bash 下运行的吗？检查 shebang 行（在脚本的开头），并确保它是#!/bin/bash，不是#!/bin/sh。并确保您没有使用sh命令 (ie sh scriptname)运行它，因为它会覆盖 shebang。
回答by potong
This might work for you:
这可能对你有用：
TESTSTRINGONE="MOTEST"
NEWTESTSTRING=${TESTSTRINGONE%"${TESTSTRINGONE#?????}"}
echo ${NEWTESTSTRING}
# MOTES
回答by Lauri
Works in most shells
适用于大多数 shell
[jaypal:~/Temp] TESTSTRINGONE="MOTEST"
[jaypal:~/Temp] sed 's/\(.\{5\}\).*//' <<< "$TESTSTRINGONE"
MOTES
回答by jaypal singh
You can try sedif you like -
喜欢的可以试试sed～
read -n 5 NEWTESTSTRING <<< "$TESTSTRINGONE"
回答by glenn Hymanman
That parameter expansion should work (what version of bash do you have?)
该参数扩展应该可以工作（你有什么版本的 bash？）
Here's another approach:
这是另一种方法：
echo $TESTSTRINGONE|awk '{print substr($ TESTSTRINGONE="MOTEST"
$ NEWTESTSTRING=$(echo ${TESTSTRINGONE::5})
$ echo $NEWTESTSTRING
MOTES
,0,5)}'
回答by Vijay
回答by amc
You were so close! Here is the easiest solution: NEWTESTSTRING=$(echo ${TESTSTRINGONE::5})
你离得太近了！这是最简单的解决方案：NEWTESTSTRING=$(echo ${TESTSTRINGONE::5})
So for your example:
所以对于你的例子：
##代码##