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27 oct. 2021 · In shell, when you see. $ command one && command two. the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash. It intends to prevent the running of the second process if the first fails.
14 sept. 2012 · This is on a current (year 2016) version of Bash, via Slackware 14.2. Whether $0 does include a path or not depends on how you ran the script in the first place. If you executed "./mytry.sh" that's what you will see in $0. If you entered "~/mytry.sh" you will see the full path (because the shell will have expanded ~).
As a string operator, = is equivalent to ==. Also, note the whitespace around = or ==: it’s required. While you can do [[ 1 == 1 ]] or [[ $(( 1+1 )) == 2 ]] it is testing the string equality — not the arithmetic equality. So -eq produces the result probably expected that the integer value of 1+1 is equal to 2 even though the right-hand side ...
1 août 2019 · echo $? # echoes 0. false. echo $? # echoes 1. From the manual: (acessible by calling man bash in your shell) Expands to the exit status of the most recently executed foreground pipeline. By convention an exit status of 0 means success, and non-zero return status means failure.
18 oct. 2013 · The =~ operator is a regular expression match operator. This operator is inspired by Perl's use of the same operator for regular expression matching. The [[ ]] is treated specially by bash; consider that an augmented version of [ ] construct: [ ] is actually a shell built-in command, which, can actually be implemented as an external command.
10 févr. 2010 · 1. In addition to previous answers, you can also use case statement to compare strings once you have a predefined set of values to choose from. For example, given that the user will provide an argument among these predefined values a or b or c or default once running the bash script, the following script demonstrates that. #!/bin/bash. case "$1 ...
In bash, && and || have equal precendence and associate to the left. See Section 3.2.3 in the manual for details. So, your example is parsed as $ (echo this || echo that) && echo other And thus only the left-hand side of the or runs, since that succeeds the right-hand side doesn't need to run.
In bash the test command will be a built-in command; try type [to learn its type. For built-in commands help will show usage, so also run help [ to see documentation. Your system probably also has a /bin/[ and a /bin/test and if you man test you can see the manuals for those.
10 oct. 2010 · 153. Just from reading that I would have never understood that "$@" expands into a list of separate parameters. Whereas, "$*" is one parameter consisting of all the parameters added together. If it still makes no sense, do this. Bash special parameters explained with four example shell scripts.
30 sept. 2010 · Bash (see conditional expressions) seems to preempt the classic and POSIX meanings for -a and -o with its own alternative operators that take arguments. With some care, you can use the more modern [[ operator, but be aware that the versions in Bash and Korn Shell (for example) need not be identical.
