Using nm to inspect static library symbols The nm command displays symbolic information from object files, libraries, and executables. It’s the standard tool for inspecting what functions and variables are defined or referenced in a static library (.a file). Basic usage List all symbols in a library: nm lib.a This outputs symbol names, but the…
Vim Regular Expressions Vim’s regex engine is powerful but requires understanding its syntax rules, which differ significantly from standard POSIX extended regex. Whether you’re doing basic substitutions or complex text transformations, knowing how Vim handles regex patterns will save you hours of frustration. Vim Regex Basics Vim supports multiple regex engines, controlled by the magic…
Background processes in Bash Spawning background processes in Bash is straightforward with the & operator, but there are several nuances depending on your use case. Basic approach The simplest method is appending & to your command: for i in $(cat ./all-hosts); do ssh “$i” “ifconfig | grep Link” & done Each & launches the process…
Calling C Functions from OCaml OCaml provides robust FFI (Foreign Function Interface) capabilities for calling C code. This is essential when you need to use existing C libraries or write performance-critical sections in C. Using the Unix Module The simplest approach for Unix/Linux system calls is the built-in Unix module, which wraps common POSIX functions…
Finding Absolute Paths from Relative Paths When working with relative paths in Linux, you often need the absolute path for scripting, logging, or passing to other programs. Several tools can resolve this, each with different strengths. Using readlink The readlink command is the traditional tool for this job. The -f flag follows symlinks and resolves…
Note: This post covers Linux fundamentals. Core concepts remain valid, but some commands and package names may differ on modern distributions. See your distro’s documentation for current details. It is common for programs to write to files in filesystems on disks. However, what if the disk was almost full when your program writes to the…
Note: This post covers Linux fundamentals. Core concepts remain valid, but some commands and package names may differ on modern distributions. See your distro’s documentation for current details. The posix_spawn() and posix_spawnp() functions create a new child process from the specified process image constructed from a regular executable file. It can be used to replace…
Note: This post covers Linux fundamentals. Core concepts remain valid, but some commands and package names may differ on modern distributions. See your distro’s documentation for current details. Programs may want to catch the kill signals sent by the kill command in C programs on Linux so that it can gracefully shutdown itself before it…
Note: This post covers C/C++ programming and debugging fundamentals. Core concepts remain valid. For current references, see cppreference.com and GDB documentation. Before statically linking you C and C++ programs, you should be aware of the drawbacks of the static linking especially with glibc. There are some good discussions already: with glibc you’re linking static programs…
Note: This post covers Linux fundamentals. Core concepts remain valid, but some commands and package names may differ on modern distributions. See your distro’s documentation for current details. It is quite common to measure the time in programs using APIs like clock() and gettimeofday(). We may also want to measure the time “accurately” for certain…
“The C language provides no built-in facilities for performing such common operations as input/output, memory management, string manipulation, and the like. Instead, these facilities are defined in a standard library, which you compile and link with your programs. The GNU C library, described in this document, defines all of the library functions that are specified…
Setting Date, Time, and Timezone in Linux Understanding and managing system time is crucial for logging, cron jobs, SSL certificates, and system synchronization. Here’s how to handle it properly on modern Linux systems. Unix Time (POSIX Time) Unix time represents seconds elapsed since 00:00:00 UTC on January 1, 1970, excluding leap seconds. Get the current…