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May 24, 2016 · -d means test if directory exists. So, if [ ! -d $directory ] means if $directory does not exist, or $directory isn't a directory (maybe a file instead). Usually this is followed by a statement to create the directory, such as. if [ ! -d $directory ]; then mkdir $directory fi
Nov 16, 2018 · If any file argument to one of the primaries is of the form /dev/fd/n, then file descriptor n is checked. If the file argument to one of the primaries is one of /dev/stdin, /dev/stdout, or /dev/stderr, file descriptor 0, 1, or 2, respectively, is checked.
Oct 11, 2023 · If you want to master the Bash shell on Linux, macOS, or another UNIX-like system, special characters (like ~, *, |, and >) are critical. We'll help you unravel these cryptic Linux command sequences and become a hero of hieroglyphics.
Mar 6, 2020 · -f and -d are file test operators options, namely:-f file is a regular file, not a directory-d file is a directory-n is comparison operator option. It returns "true" when the string following the option is not null.
If it has a meaning beyond its literal meaning, a meta-meaning, then we refer to it as a special character. Along with commands and keywords, special characters are building blocks of Bash scripts.
For instance, in your first command, the meaning of {} and \; depend on the find command (man find). The meaning of quotes on an argument to sed are dependent on either sed or bash (as it's a quoted parameter it can potentially be a shell thing). The ~/ is definitely a bash pattern expansion thing.
Jan 23, 2024 · From manipulating variables to controlling flow and accessing command line arguments, these symbols unlock the true potential of the command line. In this article, I will explore the significance and applications of Bash symbols, equipping you with the knowledge to master their usage.
Nov 19, 2019 · This tutorial will show you some of the key Linux command line technologies and introduce you to the Bash scripting language. What is Bash? Bash (short for Bourne Again SHell) is a Unix shell, ...
($0) Expands to the name of the shell or shell script. This is set at shell initialization. If Bash is invoked with a file of commands (see Shell Scripts), $0 is set to the name of that file. If Bash is started with the -c option (see Invoking Bash), then $0 is set to the first argument after the string to be executed, if one is present ...
Sep 27, 2015 · As tldp.org explains, Process substitution feeds the output of a process (or processes) into the stdin of another process. So in effect this is similar to piping stdout of one command to the other , e.g. echo foobar barfoo | wc . But notice: in the bash manpage you will see that it is denoted as <(list).
