Any good Java REPL tool/implementation?

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Any good suggestions on a Java REPL implementation like ‘scala’ and ‘python’ or ‘php -a’? The java-repl tool https://github.com/albertlatacz/java-repl/ works nicely for most situations for me. It is released as a .jar. Hence, it is easy to download and run: $ wget –quiet https://github.com/albertlatacz/java-repl/releases/download/428/javarepl-428.jar -O /tmp/javarepo-428.jar && java -jar /tmp/javarepo-428.jar One usage example is as
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How to put files with spaces in names into HDFS?

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I got this error when I tried to save a file with a space in its name into HDFS: $ hdfs dfs -put -f “/home/u1/testa/test a” “/u1/testa/test a” put: unexpected URISyntaxException while the HDFS seems allow spaces in its file names: https://hadoop.apache.org/docs/r2.7.3/hadoop-project-dist/hadoop-common/filesystem/model.html . How to achieve the effect of saving the files with spaces in
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How to get hostname in Python on Linux?

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In Python, how to get hostname as the command hostname does on Linux? In Python, you can get the hostname by the socket.gethostname() library function in the socket module: import socket hostname = socket.gethostname() Reference: https://www.systutorials.com/dtivl/20/how-to-get-the-hostname-of-the-node?show=34#a34

How to get an environment variable in Python?

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In Python, how to get an environment variable? In Python, you may use this piece of code to get an environment variable: os.environ.get(‘ENV_MIGHT_EXIST’) or this piece of code: os.getenv(‘ENV_MIGHT_EXIST’) It will return None if the environment variable is not present. Reference and for more ways, please check https://www.systutorials.com/dtivl/13/how-to-get-an-environment-variable?show=80#answer-80 .

How to read the whole file content into a string in Go?

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How to read the whole file content into a string in Go? You can use the ReadFile() func from the io/ioutil package in Go to read the whole file content: func ReadFile(filename string) ([]byte, error) For example, read file filepath content and check the error: if bytes, err := ioutil.ReadFile(filepath); err != nil { log.Fatal(“Failed
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How to set process with lowest priority?

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In system, sometimes, we need backstage threads with very very low priority since it cannot preempt any normal process asks for CPU. SCHED_IDLE class satisfies this requirement which has the priority lower than “nice=19” of CFS. Following code does this. 241 void set_idle_priority(void) { 242 struct sched_param param; 243 param.sched_priority = 0; 244 int s
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How to use ioprio_set in linux c

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Since there is no glibc wrapper for ioprio_set in linux c, we need to call this API with some definition. Using syscall in linux as follows. syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, pid, IOPRIO_PRIO_CLASS(IOPRIO_CLASS_IDLE)); Some other definitions to declare above macros. 69 enum { 70 IOPRIO_CLASS_NONE, 71 IOPRIO_CLASS_RT, 72 IOPRIO_CLASS_BE, 73 IOPRIO_CLASS_IDLE, 74 }; 75 76 enum { 77
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What is the vruntime of one process after it is moved into another run queue in Linux Kernel

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When we do migration, one process will be migrated from one source CPU’s runqueue to destination CPU’s run queue. What is the virtual run time (if CFS is used) after it is moved into destination CPU’s run queue? When the process is dequeued from source CPU’s run queue, its vruntime will minus the minimum vruntime
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Libvirt crash when upgrade from version 1.2.2 to version 2.5.0

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If you install libvirt from ubuntu software library like this sudo apt-get install libvirt-bin The default version is 1.2.2 for Ubuntu Trusty. However, after you upgrade it to version 2.5.0 from its source codes (restart the libvirtd service), you will see following error if you want to install vm with virt-install. # ./installkvm1.sh Starting install…
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Cannot start VM with error “no network with matching name ‘default'”

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I update libvirt version and want to start VM with the new libvirt tools but I failed as follows. > sudo virsh start kvm1 error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ It seems that the default ‘virbr0’ is missing after I update libvirt so I solve
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Where to download an old release package of Hadoop?

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The download page of Hadoop http://hadoop.apache.org/releases.html only contains several recent release packages. I would like to download some old release packages such as Hadoop 2.5.0 which is not available anymore on the release page. Where to download a copy of the old release? You can download the old release packages of Hadoop on the http://archive.apache.org
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How to install encfs on CentOS 6?

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I noticed your answer on configuring encfs on CentOS 6. I had difficulties installing encfs on CentOS 6. How did you install it? Thanks. For CentOS 6, I used a slightly old version (version 1.7.4) using an RPM built for by PUIAS: For x86-64 version: # yum install http://puias.princeton.edu/data/puias/6/x86_64/os/Addons/fuse-encfs-1.7.4-1.puias6.x86_64.rpm For i686 version: # yum install
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