{"id":2388,"date":"2015-07-12T23:30:55","date_gmt":"2015-07-12T15:30:55","guid":{"rendered":"http:\/\/ixyzero.com\/blog\/?p=2388"},"modified":"2015-07-12T23:30:55","modified_gmt":"2015-07-12T15:30:55","slug":"shell%e4%b8%ad%e7%9a%84%e5%a4%9a%e6%9d%a1%e4%bb%b6%e6%b5%8b%e8%af%95","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/2388.html","title":{"rendered":"shell\u4e2d\u7684[\u591a]\u6761\u4ef6\u6d4b\u8bd5"},"content":{"rendered":"<h5>\u641c\u7d22\u5173\u952e\u5b57\uff1a<\/h5>\n<ul>\n<li>shell test and\/or<\/li>\n<li>shell multi test and\/or<\/li>\n<\/ul>\n<h5>\u53c2\u8003\u89e3\u7b54\uff1a<\/h5>\n<h6><span style=\"color: #ff0000;\"><strong>\u63a8\u8350\u4f7f\u7528 &amp;&amp; \u548c ||<\/strong><\/span> \u5c06\u591a\u4e2a\u7b80\u5355\u7684\u6d4b\u8bd5\u8bed\u53e5\u8fde\u63a5\u8d77\u6765\uff1a<\/h6>\n<pre class=\"lang:default decode:true\">if [ -n \"$var\"] &amp;&amp; [ -e \"$var\"]; then\n    echo \"\\$var is not null and a file named $var exists!\"\nfi<\/pre>\n<p>\u4f7f\u7528\u4e86AND\u548cOR\u7684\u6d4b\u8bd5\u8bed\u53e5\u7684\u8fd4\u56de\u503c\u662f\u5217\u8868\u4e2d\u6700\u540e\u4e00\u4e2a\u6267\u884c\u7684\u547d\u4ee4\u7684\u8fd4\u56de\u503c\u3002<\/p>\n<ul>\n<li>\u5f53\u6267\u884c command1 &amp;&amp; command2\u00a0\u65f6\uff0c\u53ea\u6709\u5f53 command1 \u6267\u884c\u6210\u529f\u540e\u624d\u4f1a\u6267\u884c command2 \uff1b<\/li>\n<li>\u5f53\u6267\u884c command1 ||\u00a0command2\u00a0\u65f6\uff0c\u53ea\u6709\u5f53 command1 \u6267\u884c\u5931\u8d25\u540e\u624d\u4f1a\u6267\u884c command2 \u3002<\/li>\n<\/ul>\n<h6>\u4f7f\u7528&#8221;[[&#8220;\u5173\u952e\u5b57\uff08<strong>\u4e0d\u63a8\u8350<\/strong>\uff09\uff1a<\/h6>\n<p>[[\u00a0is a new improved version of &#8220;test\/[&#8220;, and is a keyword, not a program. This makes it easier to use, as shown below. [[ is understood by <a href=\"http:\/\/mywiki.wooledge.org\/KornShell\">KornShell<\/a>, Zsh and\u00a0<a href=\"http:\/\/mywiki.wooledge.org\/BASH\">BASH<\/a>\u00a0(e.g. 2.03), but not by other POSIX shell implementations (like posh, yash or dash) or the <a href=\"http:\/\/mywiki.wooledge.org\/BourneShell\">BourneShell <\/a>.<\/p>\n<p>[[ \u662f\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u4f46\u53ea\u80fd\u88ab KornShell\u3001Zsh\u548cBash \u6240\u89e3\u91ca\uff0c\u4e0d\u652f\u6301\u5176\u4ed6\u7684POSIX shell\u5b9e\u73b0\uff0c\u6bd4\u5982\uff1aposh\u3001yash\u3001dash\u6216BourneShell\uff0c\u8fd9\u6837\u7684\u8bdd\u5c31\u4e0d\u80fd\u505a\u5230\u901a\u7528\uff0c\u56e0\u6b64\u4e0d\u63a8\u8350\u4f7f\u7528\u3002<\/p>\n<pre class=\"lang:default decode:true\">$ if [[ -n \"\/tmp\" &amp;&amp; -d \"\/tmp\" ]]; then echo true; fi\ntrue\n\n$ if [ -n \"\/tmp\" &amp;&amp; -d \"\/tmp\" ]; then echo true; fi\n-bash: [: missing `]'<\/pre>\n<h6>\u5728 test\/[ \u4e2d\u4f7f\u7528-a\u548c-o\uff08<span style=\"color: #ff0000;\"><strong>\u4e0d\u63a8\u8350<\/strong><\/span>\uff09\uff1a<\/h6>\n<p>\u6d4b\u8bd5\u547d\u4ee4\u7684 AND \u548c OR \u903b\u8f91\u64cd\u4f5c\u7b26\u662f -a \u548c -o \uff1a<\/p>\n<pre class=\"lang:default decode:true\">if [ -n \"$var\" -a -e \"$var\" ] ; then\n    echo \"\\$var is not null and a file named $var exists\"\nfi<\/pre>\n<p>\u8fd9\u91cc\u6ca1\u6709 &amp;&amp; \u548c || \u7684\u8bf4\u6cd5\uff1a<\/p>\n<pre class=\"lang:default decode:true\">$ if [ -n \"\/tmp\" &amp;&amp; -d \"\/tmp\" ]; then echo true; fi  # DOES NOT WORK\nbash: [: missing `]'<\/pre>\n<blockquote>\n<p style=\"padding-left: 30px;\">In any case, avoid the -a\/-o test operators which <a href=\"http:\/\/pubs.opengroup.org\/onlinepubs\/9699919799\/utilities\/test.html#tag_20_128_16\">are deprecated and unreliable in the general case <\/a>.<\/p>\n<\/blockquote>\n<p>\u5c3d\u91cf\u907f\u514d\u5728\u6d4b\u8bd5\u64cd\u4f5c\u65f6\u4f7f\u7528 -a\/-o \u6765\u8fdb\u884c\u591a\u6761\u4ef6\u5224\u65ad\uff0c\u56e0\u4e3a\u5b83\u4eec\u5c06\u4f1a\u88ab<a href=\"http:\/\/pubs.opengroup.org\/onlinepubs\/9699919799\/utilities\/test.html#tag_20_128_16\" target=\"_blank\">\u5e9f\u5f03<\/a>\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f60\u7684\u811a\u672c\u51fa\u73b0\u95ee\u9898\uff0c\u6240\u4ee5\u4e0d\u5efa\u8bae\u5728test\/[\u4e2d\u4f7f\u7528-a\/-o\u8fdb\u884c\u591a\u6761\u4ef6\u5224\u65ad\u3002<\/p>\n<p>==<\/p>\n<h6>I want to check if [[ $var == foo || $var == bar || $var == more ]] without repeating $var n times.<\/h6>\n<p>The portable solution uses\u00a0case:<\/p>\n<pre class=\"lang:default decode:true\"># Bourne\ncase $var in\n    foo|bar|more) ... ;;\nesac<\/pre>\n<p>In Bash and ksh,\u00a0<a href=\"http:\/\/mywiki.wooledge.org\/glob\">Extended globs<\/a>\u00a0can also do this within a\u00a0[[\u00a0command:<\/p>\n<pre class=\"lang:default decode:true\"># bash\/ksh\nif [[ $var == @(foo|bar|more) ]]; then\n    ...\nfi<\/pre>\n<p>Alternatively, you may loop over a list of patterns, checking each individually.<\/p>\n<pre class=\"lang:default decode:true\"># bash\/ksh93\n[[ -v BASH_VERSION ]] &amp;&amp; shopt -s extglob\n# usage: pmatch string pattern [ pattern ... ]\nfunction any {\n    [[ -n $1 ]] || return\n    typeset pat match=$1\n    shift\n\n    for pat; do\n        [[ $match == $pat ]] &amp;&amp; return\n    done\n\n    return 1\n}\n\nvar='foo bar'\nif any \"$var\" '@(bar|baz)' foo\\* blarg; then\n    echo 'var matched at least one of the patterns!'\nfi<\/pre>\n<p>For logical conjunction (return true if\u00a0$var\u00a0matches all patterns), ksh93 can use the\u00a0&amp;\u00a0pattern delimiter.<\/p>\n<pre class=\"lang:default decode:true\"># ksh93 only\n[[ $var == @(foo&amp;bar&amp;more) ]] &amp;&amp; ...<\/pre>\n<p>For shells that support only the ksh88 subset (extglob patterns), you may\u00a0<a href=\"http:\/\/en.wikipedia.org\/wiki\/DeMorgan%27s_Law\">DeMorganify<\/a>\u00a0the logic using the negation sub-pattern operator.<\/p>\n<pre class=\"lang:default decode:true\"># bash\/ksh88\/etc...\n[[ $var == !(!(foo)|!(bar)|!(more)) ]] &amp;&amp; ...<\/pre>\n<p>But this is quite unclear and not much shorter than just writing out separate expressions for each pattern.<\/p>\n<h6>\u53c2\u8003\u94fe\u63a5\uff1a<\/h6>\n<ul>\n<li><a href=\"http:\/\/wiki.bash-hackers.org\/commands\/classictest#and_and_or\" target=\"_blank\">http:\/\/wiki.bash-hackers.org\/commands\/classictest#and_and_or<\/a><\/li>\n<li><a href=\"http:\/\/mywiki.wooledge.org\/BashPitfalls\" target=\"_blank\">http:\/\/mywiki.wooledge.org\/BashPitfalls<\/a><\/li>\n<li><a href=\"http:\/\/unix.stackexchange.com\/questions\/210763\/how-to-use-and-or-conditional-in-shell-script\" target=\"_blank\">http:\/\/unix.stackexchange.com\/questions\/210763\/how-to-use-and-or-conditional-in-shell-script<\/a><\/li>\n<li><a href=\"http:\/\/unix.stackexchange.com\/questions\/88850\/precedence-of-the-shell-logical-operators\" target=\"_blank\">http:\/\/unix.stackexchange.com\/questions\/88850\/precedence-of-the-shell-logical-operators<\/a><\/li>\n<\/ul>\n<p>=EOF=<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u641c\u7d22\u5173\u952e\u5b57\uff1a shell test and\/or shell multi test and\/or \u53c2\u8003\u89e3\u7b54\uff1a  [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,11,7],"tags":[539,65],"class_list":["post-2388","post","type-post","status-publish","format-standard","hentry","category-knowledgebase-2","category-linux","category-programing","tag-pitfalls","tag-shell"],"views":2644,"_links":{"self":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/2388","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/comments?post=2388"}],"version-history":[{"count":0,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/2388\/revisions"}],"wp:attachment":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/media?parent=2388"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/categories?post=2388"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/tags?post=2388"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}