cron runs commands on a schedule. User cron entries are edited with crontab. Edit the current user crontab Crontab format Run a script every day at 2:30 AM List existing cron jobs Use full paths inside cron jobs because the environment is usually smaller than an interactive shell.
The whatis command shows a short one-line description from the manual page database. It is useful when you know a command name but want a quick reminder of what it does. Examples For more detail, open the full manual page with man.
The renice command changes the nice value of a process that is already running. It can be useful when a process is using too much CPU or when you want to give a task lower priority. Find the process ID Lower priority of a running process A higher nice value means lower scheduling priority. Raising … Read more
GnuPG implements the OpenPGP standard and can be used to encrypt files or messages and to create digital signatures. It is still useful, but many older email-client instructions and key-generation examples are no longer current. Generate a modern key gpg –full-generate-key Choose a modern algorithm offered by your installed GnuPG version and protect the private … Read more
The which command shows the path of the executable that will run when you type a command name. It is useful when multiple versions of a tool may be installed. Basic use If the command is found in your PATH, which prints the full path. If nothing is printed, the command may not be installed … Read more
The nice command starts a program with a modified scheduling priority. It is useful when you want a background task to be less aggressive with CPU usage. Run a command with lower priority Example Higher nice values mean lower priority. To adjust a process that is already running, use renice.
cdecl and c++decl translate complicated C and C++ declarations into English and can also generate declarations from plain-language descriptions. They are useful when pointer, function-pointer, or nested type syntax becomes hard to read. Interactive mode cdecl explain int (*signal(int, int (*)(int)))(int) declare p as pointer to integer quit c++decl uses C++ terminology and syntax where … Read more
A concise cdecl reference for understanding and constructing complex C type declarations.
The install command copies files while setting ownership, permissions and target directories in one step. It is commonly used in build scripts and deployment tasks. Copy a file with permissions Create a directory with permissions For system locations such as /usr/local/bin, you may need appropriate privileges. Always check the target path before copying files.
Linux software is usually installed through the distribution package manager. This is safer than downloading random installers because packages are tracked, updated and removed cleanly. Debian and Ubuntu systems Red Hat, Fedora and similar systems Older Red Hat-based systems may use yum instead of dnf. Check whether software is already installed Prefer the package manager … Read more