I note that <system.h> is a non-standard header; I replaced it with <unistd.h> and the code compiled cleanly. When the output of your program is going to a terminal (screen), it is line buffered. When the output of your program goes to a pipe, it is fully buffered. You can control the buffering mode by … Read more
What is sh? sh (or the Shell Command Language) is a programming language described by the POSIX standard. It has many implementations (ksh88, Dash, …). Bash can also be considered an implementation of sh (see below). Because sh is a specification, not an implementation, /bin/sh is a symlink (or a hard link) to an actual … Read more
General rule: quote it if it can either be empty or contain spaces (or any whitespace really) or special characters (wildcards). Not quoting strings with spaces often leads to the shell breaking apart a single argument into many. $? doesn’t need quotes since it’s a numeric value. Whether $URL needs it depends on what you … Read more
grep -r “texthere” . The first parameter represents the regular expression to search for, while the second one represents the directory that should be searched. In this case, . means the current directory. Note: This works for GNU grep, and on some platforms like Solaris you must specifically use GNU grep as opposed to legacy … Read more
Real, User and Sys process time statistics One of these things is not like the other. Real refers to actual elapsed time; User and Sys refer to CPU time used only by the process. Real is wall clock time – time from start to finish of the call. This is all elapsed time including time … Read more
File descriptor 1 is the standard output (stdout). File descriptor 2 is the standard error (stderr). Here is one way to remember this construct (although it is not entirely accurate): at first, 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as “redirect stderr to a … Read more
How can I pretty-print JSON in a shell script?
How can I check if a directory exists in a Bash shell script?
For your case, you have one line of leading and one line of trailing context you care about, so grep -C1 Toronto input should do it.
Traditional UNIX/Linux divided everyone on Earth into three groups: The owner of the file. This is usually the file creator. The team of the owner. This is usually other members on the same project so they can share files easily. Everyone else who can get access to the system. As UNIX/Linux moved to larger platforms, … Read more