When coding, I often need to search for the references of a variable or a function across multiple files. Usually I enter command mode of vim and do a grep command, memorize the search results and open the files having hits. This common pattern could be dramatically accelerated by a user-defined vim command:
:command Gitgrep :lex system("git grep -n " . shellescape(getreg('/'))).

TL;DR The variable MAKEOVERRIDES passes the variables defined in the make command line to sub-makes (even those make invoked indirectly). Emptying MAKEOVERRIDES can prevent sub-makes from picking up variables unexpected.

GCC has its version written in the .comment section of the executable binaries as shown by commands:

objdump -s --section .comment /path/to/binary
# or pretty print
readelf -p .comment /path/to/binary

This post introduces how apply Linux commands to selective targets.

A server machine failed at upgrading from Ubuntu14.04 to Ubuntu16.04, and many packages are left in half-installed status, even apt is not working. I struggled several days to fix those broken packages, and this post documents some tricks I learnt.

I attended MPI Foundation, a nice training given by TACC staff, at the end of March. This post briefly documents the basic MPI programming knowledge I learnt (😓 should have been written long ago, but did not even start until the day before follow-up training).

This post introduces how Linux command find is used to find file or directory with certain attributes.

This post introduces how to use escape code to get colorful output in a terminal.

4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the hash code to index the “empty tree” (before your first commit) in git version control system.

This post contains three shortcuts of bash.

Tip 102:
The terminal text can be cleared by typing Ctrl+L. It is the same as the command clear.

This post contains a tip from TACC helping debug the shell script.

This post talks about how to get patch work with git.

After switched to use Linux, I use vim-latex to extand vim for LaTeX editing. However, sometimes I would encounter errors like package not found. I thought that is because vim-latex supports limited packages (under ~/.vim/ftplugin/latex-suite/packages/), but actually vim-latex is just the plugin to turn vim into a LaTeX editor, while the complier behind it is something else, for example TeX Live.
TeX Live has its own package manager called tlmgr. This post documents some issues I had to install absent package for TeX Live.

Message Passing Interface (MPI) is a standard for parallel computing, which means it could be the dependency of many programs developed for cluster. Determining the version of MPI is helpful to solve the dependency issues.

Under some circumstances, I would like to launch the process, then let other programs attach to it. No matter how fast can I type, it is impossible for me to bind the processes from the very beginning. The solution is let the script to launch the process but suspend it immediately.

#!/bin/bash
$@ &
PID=$!
kill -STOP $PID
echo $PID
wait $PID

The script earns enough time for you to do your operations in another terminal, then to resume the process:

kill -CONT $PID

Note: need to replace $PID with the number printed in the first terminal.

With huge files, tasks that as simple as removing first or last several lines could become hard. If you try to open a huge file with vim, the chance is that the system gets stuck struggling to load the huge file into memory. This post has several alternative approaches to delete lines from huge files.

To invoke an editor for a long command, try ctrl-x e (that is holding control key press x then e).

This post contains four tips from TACC making the shell command cd more versatile.

Tips about some special variables used in makefile: automatic variables, $@, $<, $^; wildcard placeholder % in targets and dependencies and $* in recipe; and .DEFAULT_GOAL.

Two useful tips from TACC tips regarding compiler macro expanding.

Tip 120:
Want to know what MACROS are predefined by the GCC and Intel compilers? Do

gcc -dM -E - < /dev/null > gcc_defined_macros.txt
icc -dM -E - < /dev/null > icc_defined_macros.txt

The flag -E in the tip is telling the compiler to expand macros.

Tip 69:
Having trouble figuring out how a macro is being expanded? Try pasting the line into a terminal and adding a -E. For example try changing mpicc -DFOO -DBAR -c foo.c into mpicc -DFOO -DBAR -E foo.c > foo.i and look at the foo.i file.

The bash-completion package does not handle command make, while we can extend the completion support for make by adding bash configurations with keyword complete.

The command line prompt in Linux could be customized to user’s need. It is achieved by modifying a series of environment variables, such as PS1, PROMPT_COMMAND and PS2.

Two tips, one to find processor information, another for detailed system configurations.
Updated with two more tips on January 23, 2018. One to find memory information, another for interrupt information.
Updated with one more tip from TACC on July 23, 2018. It gives HTML view.