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How to get lines of a file with exactly 3 characters in Linux
I need a command to find the lines of a file that have 3 characters. I do the command wc -w field.txt to list how many lines, but now I need to know the lines with 3 characters, exactly. Answer This will count (-c) the number of lines which match the regex (-E) “^.{3}$”, which is “start of l…
Building Qt apps for Windows Phone on Linux
Related to this I’m planning to develop an app for Android using Qt Quick Controls and an Android Emulator. The same set of components is said to work on Windows Phone. Thus I’d like to build the app for Windows Phone as well. Unfortunately, Qt for Windows Phone is only available for Windows. I do…
How to use Maven in a remote Linux server?
I have an extracted file of maven in my remote. I am trying to add the environment variables using these commands: When I execute mvn -version, I get this particular error : How do I run my Maven commands on Putty which I am using to access my remote Linux server? Answer Your user (z222189) doesn’t have…
How to have a separate kernel parameter for a newly created network namespace under Linux?
I am creating a new network namespace called OAM, along wit the veth interfaces to communicate between the new namespace and the default namespace: Now I check the value of ip_default_ttl parameter from within the default namespace: It is set to 64. Next I check the same parameter in the newly created OAM nam…
Why does “/usr/bin/env bash -x” only work in command line?
I am playing with a docker CentOS image, and find executing “/usr/bin/env bash -x” command is OK in terminal: But after writing this command into a script and execute it, it doesn’t work, and prompts “No such file or directory”: Is there any difference between two methods? Answer…
Rewrite at the beginning of the file
I was trying to rewriting text at beginning of file but facing the following: The header file is test.h: The source file is test.c : The main file is main.c: The make file is: The out put was expected is: But it is replacing first few characters of the first line. Where I am going wrong? Answer The output is
escape alarm() process timeout with nohup or setsid?
I have a monitoring application, Zabbix agent, that allows me to run arbitrary commands/scripts and grab the return value. The agent is configured with a timeout and any command that exceeds the timeout will be killed. For every command that is run, it first sets the timeout via alarm(timeout) and then forks …
Boosts JSON parser escapes quotation marks on MacOS but not on Linux
I have a C++ program running on a server returning JSON formatted data, serialized with boost. In some cases one value part of a JSON packet is another JSON packet serialized to string. Running in XCode on my developing machine the program returns me the value data with escaped quotation marks, compiled on th…
Linux bash printf format with color assign to variable
I just want a String (including coloring) be formatted by printf command and assign the result to a variable. Without assigning it to a variable it works fine, but as soon as I assign the result to a variable and write the result, the format is gone. My example: I found several solutions for passing the resul…