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调用 shell 命令时出现常规 awk 缓冲问题

tag-icon • tag-icon awk system-calls buffer
调用 shell 命令时出现常规 awk 缓冲问题

一些精度：

  • 常规 awk，而不是 gawk
  • AIX 6.1 和旧 shell：GNU bash，版本 2.05b.0(1)

我试图以正确的顺序显示一些内容，因此我通过 shell 的“sort”和“uniq”管道输出...但我无法按照我编写的顺序获取输出。

麻烦的代码：

egrep -i "something_FREQUENT" BIGFILE | sort | awk -F',' '
      { servs=servs $1 " " ; groupe=groupe "\n   " $2 ; }
  END { print "Groupes (alphabetical order):" ;
        printf groupe "\n" | "grep . | sort | uniq | xargs echo ";
        print ; rem="extra newline to help buffering... does NOT help.";
        system(""); rem="supposed to force flush of stdout... does NOT help.";
        print "Servers:"
        printf "%s\n", servs;
      } ' # if I add a final: "| cat" here (after "'"), does NOT help?... see last example

它输出：

Groupes (alphabetical order):

Servers:
( here a quite long list of severs... maybe until "buffer size" length? )
( etc.... but at some point :)(HERE_THE_groupe_OUTPUT)(rest of the servers here....)

??...我不知所措：似乎如果我添加：system("");在显示服务器的行之前，它也没有帮助......

同一系统上的一些相关测试：

1）类似于我的脚本：通过系统调用的“长”输出，出现乱码：

prompt$:  yes "test1" | head -10 | awk '
         { all=all "\n" $0; }
     END { print "first line:"  ;
           printf all "\n" | "sort "; 
           system(""); 
           print "last line" ;
         }'

first line:
last line

test1
test1
test1
test1
test1
test1
test1
test1
test1
test1
  # notice: the order is mixed: the shell command output is last.

2) 相同，但这次我们添加最后一个 '| cat' ：它神奇地重新排序输出......但是如果我在上面的脚本中执行相同的操作，这不会有帮助......

prompt$:  yes "test2" | head -10 | awk '
         { all=all "\n" $0; }
     END { print "first line:"  ;
           printf all "\n" | "sort "; 
           system(""); 
           print "last line" ;
         }' | cat  # ONLY ADDITION: pipe awk through cat... this HELPS here (but NOT in my script!... ??)

first line:

test2
test2
test2
test2
test2
test2
test2
test2
test2
test2
last line
  # notice: the order is OK!

答案1

您需要关闭 awk 内的管道才能将其刷新。对于第二个例子，请执行以下操作：

yes "test1" | head -10 | awk '
    { all=all "\n" $0; }
END { print "first line:"  ;
      printf all "\n" | "sort "; 
      close("sort ");
      print "last line" ;
    }'

为了使其在第一个示例中更加明显，请执行以下操作

cmd = "grep . | sort | uniq | xargs echo ";
printf groupe "\n" | cmd;
close(cmd);

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