cat | 易学教程

Fast concatenate multiple files on Linux

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问题 I am using Python multiprocessing to generate a temporary output file per process. They can be several GBs in size and I make several tens of these. These temporary files need to be concated to form the desired output and this is the step that is proving to be a bottleneck (and a parallelism killer). Is there a Linux tool that will create the concated file by modifying the file-system meta-data and not actually copy the content ? As long as it works on any Linux system that would be

Can linux cat command be used for writing text to file?

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问题 Is something like this: cat "Some text here." > myfile.txt Possible? Such that the contents of myfile.txt would now be overwritten to: Some text here. This doesn't work for me, but also doesn't throw any errors. Specifically interested in a cat -based solution (not vim/vi/emacs, etc.). All examples online show cat used in conjunction with file inputs, not raw text... 回答1: That's what echo does: echo "Some text here." > myfile.txt 回答2: Sounds like you're looking for a Here document cat >

关于node-sass安装不上的问题

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关于node-sass安装不上的问题，解决办法（链接）： https://github.com/lmk123/blog/issues/28 本人使用的是第一种方法，可行来源： CSDN 作者： dance_cat 链接： https://blog.csdn.net/dance_cat/article/details/63262831

Different show between “cat” and “vim” [closed]

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问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 6 years ago . cat /tmp/test : >> cat /tmp/test Hello World Hello World Hello World Hello World vim /tmp/test : >> vim /tmp/test ==> 1 ^[[1;31mHello World^[[0m 2 ^[[2;32mHello World^[[0m 3 ^[[5;33mHello World^[[0m 4 ^[[6;34mHello World^[[0m Sorry , I have google it , but I still don't know how to let vim /tmp/test show the

Merge two json in bash (no jq)

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问题 I have two jsons : env.json { "environment":"INT" } roles.json { "run_list":[ "recipe[splunk-dj]", "recipe[tideway]", "recipe[AlertsSearch::newrelic]", "recipe[AlertsSearch]" ] } expected output should be some thing like this : { "environment":"INT", "run_list":[ "recipe[splunk-dj]", "recipe[tideway]", "recipe[AlertsSearch::newrelic]", "recipe[AlertsSearch]" ] } I need to merge these two json (and other like these two) into one single json using only available inbuilt bash commands. only have

集成美团cat监控

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集成美团cat监控点关注不迷路，欢迎再来！最近研究spring集成美团cat监控，关于美团cat环境搭建在上篇博客已介绍，集成美团cat在对代码异常，接口请求调用次数与调用时间，sql执行时间和异常，url访问调用时间和次数进行统计，使代码可以有效的管理，在代码与sql查错和排除优化上有显著的效果，可以提升开发和运维的工作效率。有需要的朋友可以了解下。直接步入主题: CAT支持的监控消息类型包括： • Transaction 适合记录跨越系统边界的程序访问行为,比如远程调用，数据库调用，也适合执行时间较长的业务逻辑监控，Transaction用来记录一段代码的执行时间和次数。 • Event 用来记录一件事发生的次数，比如记录系统异常，它和transaction相比缺少了时间的统计，开销比transaction要小。 • Heartbeat 表示程序内定期产生的统计信息, 如CPU%, MEM%, 连接池状态, 系统负载等。 • Metric 用于记录业务指标、指标可能包含对一个指标记录次数、记录平均值、记录总和，业务指标最低统计粒度为1分钟。一.引入cat-client 的meven依赖 < dependency > < groupId > com . dianping . cat < / groupId > < artifactId > cat - client < /

How to select date range in awk

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问题 We are making a utility to ssh to different servers and collect all the error logs and send to the concerning teams this utility will cat the log file and filter using awk. e.g. cat /app1/apache/tomcat7/logs/catalina.out | awk '$0>=from&&$0<=to' from="2019-02-01 12:00" to="2019-11-19 04:50" We are saving dates in the database for last time loaded and using this date as from date in the next run. Problem awk date range given seems to be only working with yyyy-mm-dd HH:MM date format. Our log

Can you use the tac command in Terminal?

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问题 I'm trying to search a large file in reverse order from the command line (using terminal). I found the tac command: http://clifgriffin.com/2008/11/25/tac-and-reverse-grep/ tac is the inverse of cat. However, when I try to use the tac command in terminal, it says that command doesn't exist. Is there a way I'd be able to use tac in terminal? What are some other fast ways to search a file from the end via the command line? 回答1: The MacOs version of tail support the -r ("reverse") option, and

Infinite loop when redirecting file to itself from Unix cat

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问题 I'm trying to concatenate a license to the top of my built sources. I'm use GNU Make. In one of my rules, I have: cat src/license.txt build/3d-tags.js > build/3d-tags.js But this seems to be causing an infinite loop. When I kill the cat command, I see that build/3d-tags is just the contents of src/license.txt over and over again? What's going on? I would have suspected the two files to be concatenated together, and the resulting ouput from cat to be redirected back into build/3d-tags.js. I'm

Spark_rdd_and_map_reduce基本操作

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from __future__ import print_function, division from pyspark import SparkConf, SparkContext from pyspark.sql import SparkSession spark = SparkSession.builder.master( "local" ) \ .appName( "test" ) \ .enableHiveSupport() \ .getOrCreate() sc = spark.sparkContext Part1. RDD 的基本操作 RDD 由于采分散式架构，在计算以及操作是使用 Map 与 Reduce 的方式，与一般单执行绪程式逻辑不同．本节将介绍基本的 Map 与 Reduce 等基本指令，让各位同学能够熟悉如何操作 RDD． wordsList = [ 'cat' , 'elephant' , 'rat' , 'rat' , 'cat' ] wordsRDD = sc.parallelize(wordsList, 4 ) print(type(wordsRDD)) <class 'pyspark.rdd.RDD'> map (Transform) map 能將 fuction 套用在 rdd 中的每個元素上 def makePlural (word) :