How to set and get an environment variable in C on Linux? You can use the setenv and getenv POSIX APIs to set and get environment variables. To add or change environment variable: #include <stdlib.h> int setenv(const char *envname, const char *envval, int overwrite); To get value of an environment variable: #include <stdlib.h> char *getenv(const…
How to format outputs with cout in C++? You need IO Manipulators <iomanip>: Header providing parametric manipulators. There are also good tutorials on the Web: Output Formatting: http://arachnoid.com/cpptutor/student3.html Formatting Cout Output in C++ using iomanip: http://www.cprogramming.com/tutorial/iomanip.html
g++ (version g++ (GCC) 4.8.1 20130603 (Red Hat 4.8.1-1)) report: $ g++ -std=c++11 solution.cpp -o sol solution.cpp: In function ‘int main()’: solution.cpp:50:57: sorry, unimplemented: non-trivial designated initializers not supported Stat init_stat {.depth = 0, .moves = tv, .vec = init}; ^ solution.cpp:50:57: sorry, unimplemented: non-trivial designated initializers not supported solution.cpp:50:57: sorry, unimplemented: non-trivial designated initializers…
How to get a 10-byte length random string in bash. Use this script to get a 10-byte string of letters: tr -dc “[:alpha:]” < /dev/urandom | head -c 10 You can also get a string of letters or numbers: tr -dc “[:alnum:]” < /dev/urandom | head -c 10 Or printable characters except space: tr -dc…
How to trap Ctrl-C in a Bash script? The piece of code: # trap ctrl-c and call ctrl_c() trap ctrl_c INT function ctrl_c() { echo echo “Ctrl-C by user” # do the jobs exit }
I frequently hear that cin is significantly slower than scanf in C++. Is this true? And how to improve the efficiency of cin? It is really nice to use most of time. One discussion about that cin is very slow is here: http://apps.topcoder.com/forums/?module=Thread&threadID=508058&start=0&mc=7 In short: cin is not always slower (can be faster actually, see…
I am writing a OCaml program but want to call some C functions provided in some source code or library. How to achieve this? Is there any good tutorials on this? A very good tutorial that is easy to follow and understand: How to wrap C functions to OCaml. A comprehensive reference manual: Chapter 19…
Which are the consistency models used for distributed systems? Papers that survey the consistency models Robert C. Steinke and Gary J. Nutt. 2004. A unified theory of shared memory consistency. J. ACM 51, 5 (September 2004), 800-849. DOI=10.1145/1017460.1017464 http://doi.acm.org/10.1145/1017460.1017464 David Mosberger. 1993. Memory consistency models. SIGOPS Oper. Syst. Rev. 27, 1 (January 1993), 18-26. DOI=10.1145/160551.160553…
How to statically compile C and C++ projects? The compiled executable should lead no dynamical library during execution. I use gcc/g++ to compile the projects. Check this post: Statically Linking C and C++ Programs on Linux with gcc.
How to enable single sign-in for social accounts for question2answer? These servers are required: Google, Facebook, Twitter, OpenID. This site moved from Loginza to Question2Answer Open Login which works like a charm. I use the Loginza and it works very well. For Q2A, SLonoed wrote a nice plugin for loginza. How to use it: Download…
How to enable auto code completion in Vim, like in the IDE? Several plugins I use: snipMate: Plugin for using TextMate-style snippets in Vim omnicppcomplete: Plugin for C/C++ omnicompletion neocomplcache: Ultimate auto completion system for Vim
By default, Vim/Vi’s search is case sensitive. However, if I want to search case insensitively, is there any method? For example, I search for dog, instead of matching dog only case sensitively, I also want to find out phases containing Dog, DOg, etc. There are several methods: 1. Setting the search to be case insensitive…
What is the x86-64 calling convention by gcc? The calling convention of the System V AMD64 ABI is followed on GNU/Linux. The registers RDI, RSI, RDX, RCX, R8, and R9 are used for integer and memory address arguments and XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6 and XMM7 are used for floating point arguments. For…
What is the strcmp and strncmp implementation in glibc? strcmp implementation in glibc 2.16: string/strcmp.c /* Copyright (C) 1991, 1996, 1997, 2003 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU…
When developing a C++ project, debugging is an essential part of the process, as it allows you to identify and fix issues in your code. If you’re using CMake to build your project, it’s crucial to know how to enable debug mode to take advantage of debugging tools like gdb. In this post, we’ll walk…
How to get a file’s size in C? If you have the file stream (FILE * f): fseek(f, 0, SEEK_END); // seek to end of file size = ftell(f); // get current file pointer fseek(f, 0, SEEK_SET); // seek back to beginning of file // proceed with allocating memory and reading the file Or, #include…
ANSI C is a standardized version of the C programming language that was introduced in 1989 by the American National Standards Institute (ANSI). The ANSI C standard defines the syntax and semantics of the C language, including its grammar. In this post, we will explore the ANSI C grammar in more detail. The ANSI C…
We all know scanf / fscanf / sscanf is dangerous. But why? what is the exact reason? I thought the ‘%s’ is a problem that causes buffer overflow and ‘fgets’ is a better solution. But is it the exact reason? I pased a discussion by AndreyT and his discussion helps me figure it out: Claiming…
Converting a string to a long in C is a common operation that can be useful in various programming tasks. In this post, we will explore how to use the strtol and strtoul C library functions to convert a string to a long in C. Using strtol and strtoul The strtol and strtoul functions are…
By default, Vim does case sensitive search. How to make case-insensitive search in Vim? By default, Vim does case sensitive search. :set ignorecase can set Vim to conduct case insensitive search. However, it also affects substitutions, which is not we want However, how to do a case insensitive search only when it is needed? Use…