How to operator[] access element in a const map in C++?

How to operator[] access element in a const map in C++? For example, the compiler will report error on this piece of code: #include <iostream> #include <string> #include <map> std::int64_t count(const std::map<std::string, std::int64_t>& map) { return map[“one”] + map[“two”]; } int main () { std::map<std::string, std::int64_t> map = { {“one”, 1}, {“two”, 2} }; std::cout […]

How to list start and end sectors of a partition by parted in Linux?

How to list start and end of a partition by the sectors in parted on Linux? The default behavior seems be listing the start and end by bytes in parted. # parted /dev/sdc print Model: Innostor IS888 ext. HDD (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End […]

How to judge whether its STDERR is redirected to a file in a Bash script on Linux?

Within a Bash script, how to judge whether its STDERR is redirected to a file in Bash on Linux? For example, ./script.sh /tmp/log 2>&1 Can script.sh detect that its STDERR is redirected? Knowing the destination file is better. To test whether a script’s STDERR (or STDOUT) is redirected to a file, check by [[ -f […]

How can I login without password and run command in server at a local machine remotely?

Login without PWD is fast and efficient. Running commands in server from local machine also have these benefits. login without PWD: add PC A’s public key to PC B’s authorized keys. > a@A:~> cat .ssh/id_rsa.pub | ssh b@B ‘cat >> .ssh/authorized_keys’ > b@B’s password: Run command remotely ssh root@MachineB “ls” NOTE: running commands remotely is […]

How to check interrupts lively in your systems?

I need to see what kind of interrupts are handled by which CPU. Please run command: # cat /proc/interrupts or you can execute $ watch -n1 “cat /proc/interrupts” to watch interrupts every 1 second. See [1] [2] for more details. References: [1] https://stackoverflow.com/questions/28301875/how-to-observe-interrupts-in-windows-or-linux-ubuntu-14-04 [2] http://www.linuxjournal.com/content/watch-live-interrupts Answered by harryxiyou.

How to find out all files with replication factor 1 in HDFS?

How to find out all files with replication factor 1 in HDFS? The hdfs dfsadmin -report shows there are blocks with replication factor 1: Missing blocks (with replication factor 1): 7 How to find them out? You can run hdfs fsck to list all files with their replication counts and grep those with replication factor […]

How to detect whether a file is being written by any other process in Linux?

How to detect whether a file is being written by any other process in Linux? Before a program open a file to processes it, it wants to ensure no other processes are writing to it. Here, we are sure after the files are written and closed, they will not be written any more. Hence, one-time […]

How to get the highest temperature from all sensors in a server on Linux?

It is useful to monitor a server node’s temporary. Among all the sensors’ temperatures, the higher one may be a very important one. How to get the highest temperature from all sensors in a server on Linux? You can use this command to get the the highest temperature from all sensors in a server on […]