testsandcomparisons.html
来自「BASH Shell 编程 经典教程 《高级SHELL脚本编程》中文版」· HTML 代码 · 共 190 行
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><HTML><HEAD><TITLE>测试和比较: 一种可选的方法</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINKREL="HOME"TITLE="高级Bash脚本编程指南"HREF="index.html"><LINKREL="UP"TITLE="杂项"HREF="miscellany.html"><LINKREL="PREVIOUS"TITLE="Shell包装"HREF="wrapper.html"><LINKREL="NEXT"TITLE="递归"HREF="recursionsct.html"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#0000FF"VLINK="#840084"ALINK="#0000FF"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">高级Bash脚本编程指南: 一本深入学习shell脚本艺术的书籍</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="wrapper.html"ACCESSKEY="P">前一页</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">33. 杂项</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="recursionsct.html"ACCESSKEY="N">下一页</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="TESTSANDCOMPARISONS">33.3. 测试和比较: 一种可选的方法</A></H1><P>对于测试来说, <AHREF="testconstructs.html#DBLBRACKETS">[[ ]]</A>结构可能比<KBDCLASS="USERINPUT">[ ]</KBD>结构更合适. 同样地, 在算术比较中, 使用<AHREF="dblparens.html">(( ))</A>结构可能会更有用. <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><FONTCOLOR="#000000"><PRECLASS="PROGRAMLISTING"> 1 a=8 2 3 # 下面所有的比较都是等价的. 4 test "$a" -lt 16 && echo "yes, $a < 16" # "与列表" 5 /bin/test "$a" -lt 16 && echo "yes, $a < 16" 6 [ "$a" -lt 16 ] && echo "yes, $a < 16" 7 [[ $a -lt 16 ]] && echo "yes, $a < 16" # 在[[ ]]和(( ))结构中, 8 (( a < 16 )) && echo "yes, $a < 16" # 不用将变量引用起来. 9 10 city="New York" 11 # 同样地, 下面所有的比较都是等价的. 12 test "$city" \< Paris && echo "Yes, Paris is greater than $city" # 按照ASCII顺序比较. 13 /bin/test "$city" \< Paris && echo "Yes, Paris is greater than $city" 14 [ "$city" \< Paris ] && echo "Yes, Paris is greater than $city" 15 [[ $city < Paris ]] && echo "Yes, Paris is greater than $city" # 不需要引用$city. 16 17 # 感谢, S.C. </PRE></FONT></TD></TR></TABLE></P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="wrapper.html"ACCESSKEY="P">前一页</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html"ACCESSKEY="H">首页</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="recursionsct.html"ACCESSKEY="N">下一页</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">Shell包装</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="miscellany.html"ACCESSKEY="U">上一级</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">递归</TD></TR></TABLE></DIV></BODY></HTML>⌨️ 快捷键说明
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