ack-grep Regex 没有返回一致的结果
ack-grep Regex not returning consistent results
我在 bash 脚本中执行以下 ack-grep，虽然它 大部分 工作..我得到不一致的结果。我使用的线路是：
ack-grep '(?<=imageserver).*(?=png)'
这是 Perl 类型的正则表达式（ack_grep 和普通 grep 都支持）——我正在搜索 imageserver 和 png 之间的所有内容。虽然它 大部分 有效——我得到不一致的结果 IE:
为什么您会看到它匹配前无数行，然后匹配它（理论上）应该有两到三个匹配项的内容。很明显最后一个 "block" should 在 png 的 first 迭代之后匹配但是它跳过了它多次并且终于落定了——
因此，返回的第一对是我想要的结果 -- 最后突出显示的块是 "bad" 结果。我如何在这里获得一致的结果？我会为 copy/paste 后代粘贴一些 returns 这个结果的文本（可验证的例子）。如果您将以下内容复制并粘贴到文本文件中，您应该会得到与我相同的结果。
这是语法错误、误解还是错误？讨厌应该工作但不工作的时候......发展的祸根。
.mobile_menu_icon { display:block;cursor:pointer;width:100%;height:40px;margin:0 auto;background-image:url('/imageserver/default_images/four_lines_40x19.png');
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.button-finished { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/checkmark.png') no-repeat;background-size:16px 16px;background-position:center; }
background:url('/imageserver/confirm/ie.png');
background:url('/imageserver/confirm/buttons.png') no-repeat;
background:url('/imageserver/confirm/buttons.png') no-repeat;
.capItem { width:30px;height:30px;background:url('/imageserver/styles/captchaShapesWhite.png');background-repeat:no-repeat;background-size:auto 35px;display:inline-block;margin:0 3px; }
.form_button_error { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/deleteIcon.png') no-repeat;background-size:13px 13px;background-position:center;opacity:1;transition:all ease-in-out 150ms; }
.form_button_finished { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/checkmark.png') no-repeat;background-size:16px 16px;background-position:center; }
#mega_slider_wrapper,.shadow{width:100%;position:relative}.nav-arrows,.nav-dots,.shadow{display:none}.nav-arrows a,.nav-dots span,.nav-options span{cursor:pointer;border-radius:50%}#mega_slider_wrapper{background:0 0;overflow:hidden}#mega_slider_wrapper img,.mega_slide_image{width:100%}.shadow{height:168px;margin-top:-110px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/shadow.png) bottom center no-repeat;background-size:100% 100%;z-index:-1}.sb-description h3{text-shadow:1px 1px 1px rgba(0,0,0,.3)}.sb-description h3 a{color:#4a3c27;text-shadow:0 1px 1px rgba(255,255,255,.5)}.nav-arrows a{width:42px;height:42px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/nav.png) top left no-repeat #cbbfae;position:absolute;top:50%;left:2px;text-indent:-9000px;opacity:.9;box-shadow:0 1px 1px rgba(255,255,255,.8)}.nav-arrows a:first-child{left:auto;right:2px;background-position:top right}.nav-arrows a:hover{opacity:1}.nav-dots{text-align:center;position:absolute;height:30px;width:100%;left:0}.nav-dots span{display:inline-block;width:16px;height:16px;margin:3px;box-shadow:0 1px 1px rgba(255,255,255,.6),inset 0 1px 1px rgba(0,0,0,.1)}.nav-dots span.nav-dot-current{box-shadow:0 1px 1px rgba(255,255,255,.6),inset 0 1px 1px rgba(0,0,0,.1),inset 0 0 0 3px #cbbfae,inset 0 0 0 8px #fff}.nav-options{width:70px;height:30px;position:absolute;right:70px;bottom:0;display:none}.nav-options span{width:30px;height:30px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/options.png) top left no-repeat #cbbfae;text-indent:-9000px;opacity:.7;display:inline-block}.sb-slider,.sb-slider li>img{width:100%}.nav-options span:first-child{background-position:-30px 0;margin-right:3px}.nav-options span:hover{opacity:1}.sb-slider{margin:0 auto;position:relative;overflow:hidden;list-style-type:none;padding:0;max-width:2000px!important}.sb-slider li{margin:0;padding:0;display:none}.sb-slider li>a{outline:0}.sb-slider img{max-width:100%;display:block}.sb-description{width:100%;max-width:1124px;margin:0 auto;padding:30px 10px 10px;height:900px;top:0;left:10px;right:10px;z-index:10;position:absolute;color:#fff;-webkit-transition:all .2s;-moz-transition:all .2s;-o-transition:all .2s;-ms-transition:all .2s;transition:all .2s;background:rgba(40,40,40,.2);text-shadow:#000 0 0 7px}.sb-description h2,.sb-description h3{line-height:1.1;margin:4px 0;padding:4px 0}.nav-dots span,.slider_button{transition:all ease-in-out 180ms}.sb-description h2{font-size:42px}.sb-description h3{font-size:22px}.sb-perspective{position:relative}.sb-perspective>div{position:absolute;-webkit-transform-style:preserve-3d;-moz-transform-style:preserve-3d;-o-transform-style:preserve-3d;-ms-transform-style:preserve-3d;transform-style:preserve-3d;-webkit-backface-visibility:hidden;-moz-backface-visibility:hidden;-o-backface-visibility:hidden;-ms-backface-visibility:hidden;backface-visibility:hidden}.sb-side{margin:0;display:block;position:absolute;-moz-backface-visibility:hidden;-webkit-transform-style:preserve-3d;-moz-transform-style:preserve-3d;-o-transform-style:preserve-3d;-ms-transform-style:preserve-3d;transform-style:preserve-3d}.nav-arrows,.nav-arrows a,.nav-dots{z-index:11!important}.nav-arrows a{margin-top:-60px!important;background-color:rgba(0,0,0,.8);margin-left:10px;margin-right:10px}.nav-dots{bottom:0!important;background:rgba(0,0,0,.8);padding:8px}.nav-dots span{background:#777}.nav-dots span:hover{background:#aaa}.slider_button{position:relative;display:inline-block;line-height:1;width:auto;padding:10px 16px;background:#1F1E1E;border-radius:5px;color:#fff;text-decoration:none;margin:12px 0 0;font-size:16px}.slider_button:hover{background:#333}@media (max-width:1170px){.sb-description{width:85%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}}@media (max-width:850px){.sb-description{width:80%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}.sb-description h2,.sb-description h3{line-height:1.1;margin:4px 0;padding:4px 0}.sb-description h2{font-size:28px}.sb-description h3{font-size:14px}}@media (max-width:650px){.sb-description{width:75%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}}@media (max-width:600px){.hide_in_mobile{display:none}}
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您的正则表达式版本的问题在于它是贪婪的，这意味着 .* 消耗所有字符直到行尾，然后执行回溯。这就是为什么在你的破损部分（长黄线）表达式匹配 'imageserver' 和 last 'png' 之间的所有内容。
稍微修改一下就可以让你的正则表达式变得非贪婪；只需在量词后添加一个 ? 即可。然后，新的正则表达式还将搜索前面的 'imageserver'，但如果后面有 'png' 序列，它会直接检查每个后续字符。因此，它只消耗和匹配 first 'png' 序列之前的文本。
可以在此处找到新正则表达式 (?<=imageserver).*?(?=png) 和您的文本的示例：https://regex101.com/r/FvSwg4/1
查看示例的正则表达式调试器视图也是一个好主意。这样就可以更好地理解为匹配必须执行的单个步骤。
我在 bash 脚本中执行以下 ack-grep，虽然它 大部分 工作..我得到不一致的结果。我使用的线路是：
ack-grep '(?<=imageserver).*(?=png)'
这是 Perl 类型的正则表达式（ack_grep 和普通 grep 都支持）——我正在搜索 imageserver 和 png 之间的所有内容。虽然它 大部分 有效——我得到不一致的结果 IE:
为什么您会看到它匹配前无数行，然后匹配它（理论上）应该有两到三个匹配项的内容。很明显最后一个 "block" should 在 png 的 first 迭代之后匹配但是它跳过了它多次并且终于落定了——
因此，返回的第一对是我想要的结果 -- 最后突出显示的块是 "bad" 结果。我如何在这里获得一致的结果？我会为 copy/paste 后代粘贴一些 returns 这个结果的文本（可验证的例子）。如果您将以下内容复制并粘贴到文本文件中，您应该会得到与我相同的结果。
这是语法错误、误解还是错误？讨厌应该工作但不工作的时候......发展的祸根。
.mobile_menu_icon { display:block;cursor:pointer;width:100%;height:40px;margin:0 auto;background-image:url('/imageserver/default_images/four_lines_40x19.png');
.button-error { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/deleteIcon.png') no-repeat;background-size:16px 16px;background-position:center;opacity:1;transition:all ease-in-out 150ms; }
.button-finished { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/checkmark.png') no-repeat;background-size:16px 16px;background-position:center; }
background:url('/imageserver/confirm/ie.png');
background:url('/imageserver/confirm/buttons.png') no-repeat;
background:url('/imageserver/confirm/buttons.png') no-repeat;
.capItem { width:30px;height:30px;background:url('/imageserver/styles/captchaShapesWhite.png');background-repeat:no-repeat;background-size:auto 35px;display:inline-block;margin:0 3px; }
.form_button_error { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/deleteIcon.png') no-repeat;background-size:13px 13px;background-position:center;opacity:1;transition:all ease-in-out 150ms; }
.form_button_finished { display:inline-block;width:14px;height:13px;background:url('/imageserver/GlobalMedia/Icons/checkmark.png') no-repeat;background-size:16px 16px;background-position:center; }
#mega_slider_wrapper,.shadow{width:100%;position:relative}.nav-arrows,.nav-dots,.shadow{display:none}.nav-arrows a,.nav-dots span,.nav-options span{cursor:pointer;border-radius:50%}#mega_slider_wrapper{background:0 0;overflow:hidden}#mega_slider_wrapper img,.mega_slide_image{width:100%}.shadow{height:168px;margin-top:-110px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/shadow.png) bottom center no-repeat;background-size:100% 100%;z-index:-1}.sb-description h3{text-shadow:1px 1px 1px rgba(0,0,0,.3)}.sb-description h3 a{color:#4a3c27;text-shadow:0 1px 1px rgba(255,255,255,.5)}.nav-arrows a{width:42px;height:42px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/nav.png) top left no-repeat #cbbfae;position:absolute;top:50%;left:2px;text-indent:-9000px;opacity:.9;box-shadow:0 1px 1px rgba(255,255,255,.8)}.nav-arrows a:first-child{left:auto;right:2px;background-position:top right}.nav-arrows a:hover{opacity:1}.nav-dots{text-align:center;position:absolute;height:30px;width:100%;left:0}.nav-dots span{display:inline-block;width:16px;height:16px;margin:3px;box-shadow:0 1px 1px rgba(255,255,255,.6),inset 0 1px 1px rgba(0,0,0,.1)}.nav-dots span.nav-dot-current{box-shadow:0 1px 1px rgba(255,255,255,.6),inset 0 1px 1px rgba(0,0,0,.1),inset 0 0 0 3px #cbbfae,inset 0 0 0 8px #fff}.nav-options{width:70px;height:30px;position:absolute;right:70px;bottom:0;display:none}.nav-options span{width:30px;height:30px;background:url(/imageserver/AdminMedia/moduleImages/megaslider/options.png) top left no-repeat #cbbfae;text-indent:-9000px;opacity:.7;display:inline-block}.sb-slider,.sb-slider li>img{width:100%}.nav-options span:first-child{background-position:-30px 0;margin-right:3px}.nav-options span:hover{opacity:1}.sb-slider{margin:0 auto;position:relative;overflow:hidden;list-style-type:none;padding:0;max-width:2000px!important}.sb-slider li{margin:0;padding:0;display:none}.sb-slider li>a{outline:0}.sb-slider img{max-width:100%;display:block}.sb-description{width:100%;max-width:1124px;margin:0 auto;padding:30px 10px 10px;height:900px;top:0;left:10px;right:10px;z-index:10;position:absolute;color:#fff;-webkit-transition:all .2s;-moz-transition:all .2s;-o-transition:all .2s;-ms-transition:all .2s;transition:all .2s;background:rgba(40,40,40,.2);text-shadow:#000 0 0 7px}.sb-description h2,.sb-description h3{line-height:1.1;margin:4px 0;padding:4px 0}.nav-dots span,.slider_button{transition:all ease-in-out 180ms}.sb-description h2{font-size:42px}.sb-description h3{font-size:22px}.sb-perspective{position:relative}.sb-perspective>div{position:absolute;-webkit-transform-style:preserve-3d;-moz-transform-style:preserve-3d;-o-transform-style:preserve-3d;-ms-transform-style:preserve-3d;transform-style:preserve-3d;-webkit-backface-visibility:hidden;-moz-backface-visibility:hidden;-o-backface-visibility:hidden;-ms-backface-visibility:hidden;backface-visibility:hidden}.sb-side{margin:0;display:block;position:absolute;-moz-backface-visibility:hidden;-webkit-transform-style:preserve-3d;-moz-transform-style:preserve-3d;-o-transform-style:preserve-3d;-ms-transform-style:preserve-3d;transform-style:preserve-3d}.nav-arrows,.nav-arrows a,.nav-dots{z-index:11!important}.nav-arrows a{margin-top:-60px!important;background-color:rgba(0,0,0,.8);margin-left:10px;margin-right:10px}.nav-dots{bottom:0!important;background:rgba(0,0,0,.8);padding:8px}.nav-dots span{background:#777}.nav-dots span:hover{background:#aaa}.slider_button{position:relative;display:inline-block;line-height:1;width:auto;padding:10px 16px;background:#1F1E1E;border-radius:5px;color:#fff;text-decoration:none;margin:12px 0 0;font-size:16px}.slider_button:hover{background:#333}@media (max-width:1170px){.sb-description{width:85%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}}@media (max-width:850px){.sb-description{width:80%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}.sb-description h2,.sb-description h3{line-height:1.1;margin:4px 0;padding:4px 0}.sb-description h2{font-size:28px}.sb-description h3{font-size:14px}}@media (max-width:650px){.sb-description{width:75%!important;min-width:auto!important;margin:0 60px;box-sizing:border-box}}@media (max-width:600px){.hide_in_mobile{display:none}}
<div class="logo"><a href="/"><img src="/imageserver/UserMedia/zakattack/Logo.png" /></a></div>
<div class="mobile_logo"><a href="/"><img src="/imageserver/UserMedia/zakattack/mobile.png" alt="Logo" /></a></div>
<div class="powered_by">Powered by <a href="http://yourwebpro.com" target="new"><img src="/imageserver/UserMedia/ywpgallery/ywpLogo.png" style="max-height:25px;vertical-align:middle;" alt="Your Web Pro | Roofing and Contractor Websites" title="On-Line Showrooms for Roofers & Contractors"></a></div>
您的正则表达式版本的问题在于它是贪婪的，这意味着 .* 消耗所有字符直到行尾，然后执行回溯。这就是为什么在你的破损部分（长黄线）表达式匹配 'imageserver' 和 last 'png' 之间的所有内容。
稍微修改一下就可以让你的正则表达式变得非贪婪；只需在量词后添加一个 ? 即可。然后，新的正则表达式还将搜索前面的 'imageserver'，但如果后面有 'png' 序列，它会直接检查每个后续字符。因此，它只消耗和匹配 first 'png' 序列之前的文本。
可以在此处找到新正则表达式 (?<=imageserver).*?(?=png) 和您的文本的示例：https://regex101.com/r/FvSwg4/1
查看示例的正则表达式调试器视图也是一个好主意。这样就可以更好地理解为匹配必须执行的单个步骤。