如何在shell脚本中检测BSD与GNU版本的日期 [英] How can I detect BSD vs. GNU version of date in shell script
问题描述
是测试操作系统类型的最优雅的方式,所以我可以发送正确的日期标记?
编辑:
To澄清,我的目标是使用在BSD和GNU中看起来不同的日期相对日期计算工具。
BSD示例
date -v -1d
GNU示例
date --date =1天前
使用便携式标志。该标准可用此处
对于打印相对日期的特殊问题,使用perl比日期更容易:
perl -E'说标量本地时间(时间 - 86400)'
(注意这个解决方案完全失败23或25小时的时间,但是许多perl解决方案可以解决这个问题,请参见perl常见问题。)
但是你一定可以使用Keith的想法和做法:
如果date -v 1d> / dev / null 2>& 1;那么
DATE ='date -v 1d'
else
DATE ='date --date =1天前'
fi
eval $ DATE
或只是
DATE = $(date -v 1d> / dev / null 2>& 1)|| DATE = $(date --date =1天前)
I am writing a shell script that needs to do some date string manipulation. The script should work across as many *nix variants as possible, so I need to handle situations where the machine might have the BSD or the GNU version of date.
What would be the most elegant way to test for the OS type, so I can send the correct date flags?
EDIT: To clarify, my goal is to use date's relative date calculation tools which seem distinct in BSD and GNU.
BSD example
date -v -1d
GNU example
date --date="1 day ago"
Use portable flags. The standard is available here
For the particular problem of printing a relative date, it is probably easier to use perl than date:
perl -E 'say scalar localtime( time - 86400 )'
(note that this solution utterly fails on 23 or 25 hour days, but many perl solutions are available to address that problem. See the perl faq.)
but you could certainly use a variation of Keith's idea and do:
if date -v 1d > /dev/null 2>&1; then
DATE='date -v 1d'
else
DATE='date --date="1 day ago"'
fi
eval $DATE
or just
DATE=$(date -v 1d > /dev/null 2>&1) || DATE=$(date --date="1 day ago")
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