How to remove newline characters from a string in C++? For example, a string like line 1 line 3 line 4 should be converted to line 1line 3line 4 In short, use this code snippet: input.erase(std::remove(input.begin(), input.end(), ‘\n’), input.end()); std::remove() shifts all elements that are equal to the value n by moving the elements in […]
SysTutorials
1209 posts in total.
How to change the default target of `make`?
The default target of make is the first target. But can I change the default target in Makefile and how to change the default target of make? The default goal of make is the first target whose name does not start with ‘.’ if .DEFAULT_GOAL is not set. Ref: make manual. To set the default […]
How to get one process’s port number?
If we want to check one program on one remote server, we need to know this server’s IP and port number. How to get this program’s port number in the remote server? # netstat -tulpn Remember to run this program with root permission since some programs can only be accessed by root. Answered by harryxiyou.
how to list and delete shared memory in linux?
how to list and delete shared memory in linux? List all shared memories in your Linux Systems > $ ipcs -m Delete specific one > $ ipcrm -M 0x0001869c Answered by harryxiyou.
What are the differences between BIOS and UEFI?
BIOS: Basic Input Output Systems UEFI: Unified Extensible Firmware Interface UEFI is the advanced BIOS, which solves some limitations in BIOS such as 1, 16-bit processor mode; 2, 1 MB addressable space and PC AT hardware. References: https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface Answered by harryxiyou.
Latex is stuck with a strange problem, see more information for details.
$ make pdflatex main.tex This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015/Debian) (preloaded format=pdflatex) restricted write18 enabled. entering extended mode (./main.tex LaTeX2e <2016/02/01> Babel <3.9q> and hyphenation patterns for 81 language(s) loaded. (/usr/share/texlive/texmf-dist/tex/latex/base/article.cls Document Class: article 2014/09/29 v1.4h Standard LaTeX document class (/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo)) (./usenix.sty (/usr/share/texlive/texmf-dist/tex/latex/psnfss/mathptmx.sty)) (/usr/share/texlive/texmf-dist/tex/latex/graphics/epsfig.sty (/usr/share/texlive/texmf-dist/tex/latex/graphics/graphicx.sty (/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty) (/usr/share/texlive/texmf-dist/tex/latex/graphics/graphics.sty (/usr/share/texlive/texmf-dist/tex/latex/graphics/trig.sty) (/usr/share/texlive/texmf-dist/tex/latex/latexconfig/graphics.cfg) (/usr/share/texlive/texmf-dist/tex/latex/pdftex-def/pdftex.def (/usr/share/texlive/texmf-dist/tex/generic/oberdiek/infwarerr.sty) (/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ltxcmds.sty))))) (/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifpdf.sty) […]
What are the differences between NUMA architecture and SMP architecture?
NUMA Architecture: Non-Uniform Memory Access architecture. SMP: Symmetric Multiprocessing architecture. In a Symmetric Multiprocessor, the architectural “distance” to any memory location is the same for all processors, i.e. “symmetric”. In a NonUniform Memory Access machine, each processor is “closer” to some memory locations than others; i.e. memory is partitioned among them Asymmetrically. From my understanding, […]
How to get a server’s serial number remotely?
How to get a server’s serial number remotely? Tested on Linux Ubuntu 14.04 Trusty > sudo apt-get install dmidecode > sudo dmidecode -s system-serial-number Answered by harryxiyou. I tried this on several Linux boxes with CentOS 7 and it seems A physical node returns a string like System Serial Number. A KVM VM returns a […]
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 […]
Why do I need to run latex/bibtex three times to make everything look good?
Why does latex need to be executed 3 times like following? pdflatex main.tex bibtex main pdflatex main.tex pdflatex main.tex Copied from https://tex.stackexchange.com/questions/53235/why-does-latex-bibtex-need-three-passes-to-clear-up-all-warnings. The reason is as follows: 1, At the first latex run, all cite{…} arguments are written in the file document.aux. 2, At the bibtex run, this information is taken by bibtex and the […]
What is the difference between work conserving I/O scheduler and non-work conserving I/O scheduler?
What is the difference between work conserving I/O scheduler and non-work conserving I/O scheduler? In a work-conserving mode, the scheduler must choose one of the pending requests, if any, to dispatch, even if the pending requests are far away from the current disk head position. The rationale for non-work-conserving schedulers, such as the anticipatory scheduler […]
diff alternative on Windows to find differences between 2 files?
diff on Linux is a very handy tool. Any good diff alternatives on Windows to find differences between 2 files? A GUI program will be better on Windows. I would recommend meld for Windows users. Meld is a visual diff and merge tool open source software. meld is available on Linux, Windows and Mac OS […]
how to set linux date and time in commands
how to set linux date and time in commands For example, to change date to 14 Nov 2017 11:57:00, the command would be, $ sudo date –set “14 Nov 2017 11:57:00” Tue Nov 14 11:57:00 HKT 2017 Answered by harryxiyou.
In Python, `os.makedirs()` with 0777 mode does not give others write permission
In Python, os.makedirs() with 0777 mode can not give others write permission The code is as follows $ python Python 2.7.5 (default, Aug 4 2017, 00:39:18) [GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux2 Type “help”, “copyright”, “credits” or “license” for more information. >>> import os >>> os.makedirs(“/tmp/test1/test2”, 0777) >>> The created dirs are not […]
autohide top and bottom panel in RHEL 7
How to autohide top and bottom panels in RHEL 7 while application is running I don’t think GNOME 3 or GNOME 3 classic has this function available or there any plugins that supports so. If you need this function that the panel can hide automatically, you may consider another desktop environment, such as MATE, that […]
How to install alien on CentOS 7 to convert .deb to .rpm?
How to install the alien command on CentOS 7 to convert .deb to .rpm? alien is already in EPEL and it makes it quite easy to install it in CentOS 7. First, enable EPEL following this tutorials. Then, install alien by # yum install alien Then alien should be ready: # yum info alien Installed […]
How to force a fsck during next rebooting of Linux?
How to force a fsck of a file system, say the root, during the next rebooting of Linux? 2 possible ways: /forcefsck way for / # touch /forcefsck and reboot. Next time the / will be fsck’ed . systemd way Add these 2 kernel boot parameters: fsck.mode=force fsck.repair=yes What these 2 kernel parameters do: KERNEL […]
How to force a checkpointing of metadata in HDFS?
HDFS SecondaraNameNode log shows 2017-08-06 10:54:14,488 ERROR org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode: Exception in doCheckpoint java.io.IOException: Inconsistent checkpoint fields. LV = -63 namespaceID = 1920275013 cTime = 0 ; clusterId = CID-f38880ba-3415-4277-8abf-b5c2848b7a63 ; blockpoolId = BP-578888813-10.6.1.2-1497278556180. Expecting respectively: -63; 263120692; 0; CID-d22222fd-e28a-4b2d-bd2a-f60e1f0ad1b1; BP-622207878-10.6.1.2-1497242227638. at org.apache.hadoop.hdfs.server.namenode.CheckpointSignature.validateStorageInfo(CheckpointSignature.java:134) at org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode.doCheckpoint(SecondaryNameNode.java:531) at org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode.doWork(SecondaryNameNode.java:395) at org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode$1.run(SecondaryNameNode.java:361) at org.apache.hadoop.security.SecurityUtil.doAsLoginUserOrFatal(SecurityUtil.java:415) at org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode.run(SecondaryNameNode.java:357) It seems the checkpoint […]
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.
