You cannot have spaces around the = sign. When you write: STR = “foo” bash tries to run a command named STR with 2 arguments (the strings = and foo) When you write: STR =foo bash tries to run a command named STR with 1 argument (the string =foo) When you write: STR= foo bash … 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
Once you grasp that [ is a command, a whole lot becomes clearer! [ is another way to spell “test“. help [ However while they do exactly the same, test turns out to have a more detailed help page. Check help test …for more information. Furthermore note that I’m using, by intention, help test and … Read more
#Getting shell variables into awk may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below. v1.5 Using -v (The best way, most portable) Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk … Read more
Yes. Bash scripts are sensitive to line-endings, both in the script itself and in data it processes. They should have Unix-style line-endings, i.e., each line is terminated with a Line Feed character (decimal 10, hex 0A in ASCII). DOS/Windows line endings in the script With Windows or DOS-style line endings , each line is terminated … Read more
Single quotes won’t interpolate anything, but double quotes will. For example: variables, backticks, certain \ escapes, etc. Example: $ echo “$(echo “upg”)” upg $ echo ‘$(echo “upg”)’ $(echo “upg”) The Bash manual has this to say: 3.1.2.2 Single Quotes Enclosing characters in single quotes (‘) preserves the literal value of each character within the quotes. … Read more
for i in $(seq 1 $END); do echo $i; done edit: I prefer seq over the other methods because I can actually remember it 😉
You can enter the long form command: source ~/.bashrc or you can use the shorter version of the command: . ~/.bashrc
In addition to backticks `command`, command substitution can be done with $(command) or “$(command)”, which I find easier to read, and allows for nesting. OUTPUT=$(ls -1) echo “${OUTPUT}” MULTILINE=$(ls \ -1) echo “${MULTILINE}” Quoting (“) does matter to preserve multi-line variable values; it is optional on the right-hand side of an assignment, as word splitting … Read more
How do I parse command line arguments in Bash?