awk - Unix, Linux Command---reference
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</tr> </tr> </tr> </tr> </tr> </tr> </tr> Control StatementsThe control statements are as follows: <table class="src" cellspacing="5" cellpadding="5"> | Description | file?[,?how]) how?should only be used when closing one end of a two-way pipe to a co-process. It must be a string value,either?"to"?or?"from".file file; set?NF.?var var?from next input record; set?NR,?FNR.?var?<file var?from next record of?file.command?| getline?[var]command?piping the output either into?$0?or?var,as above.command?|& getline?[var]command?as a co-process piping the output either into?$0or?var,as above. Co-processes are a?gawk?extension.?expr-list ?expr-list?>file file. Each expression is separated by the value of the?OFS?variable. The output record is terminated with the value of the?ORS?variable.?fmt,expr-list ?fmt,expr-list?>file file.cmd-line) cmd-line,and return the exit status. (This may not be available on non-POSIX?systems.)file]) file. If?file?is missing,then standard output is flushed. If?file?is the null string,then all open output files and pipes have their buffers flushed.（编辑：晋中站长网）
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