2017年1月27日 · help [[returns useful information—since [[an internal bash command—but does not say whether =~ uses basic or extended regex syntax. ⋯ The text you quoted is from the bash man page. I realize you said “read the bash man pages” but at first, I thought you meant read the man pages within bash.

The -s test returns true if [...] if file exists and has a size greater than zero. This is documented in the bash manual, and also in the manual for the test utility (the test may also be written if test -s file; then).

2011年8月26日 · There's a simpler way of what you're doing. If you use set -x (or set -o xtrace - same thing), the script will automatically echo each line before it's executed.

2017年8月31日 · When bash is a non-interactive shell which is run by an RSH or SSH daemon (typically because you run ssh host.example.com somecommand and bash is your login shell on host.example.com). When it's invoked explicitly, e.g. in a user's .bash_profile (bash's choice of startup files is a bit weird). [ -t 1 ] is a poor way to detect interactive shells ...

2014年7月30日 · The easy way to check that a string only contains characters in an authorized set is to test for the presence of unauthorized characters. Thus, instead of testing whether the string only contains spaces, test whether the string contains some character other than space. In bash, ksh or zsh:

You can find a very nice reference for bash's [aka test builtin's operators here, or by running help test in a bash shell or info bash test or info bash '[' from any shell¹. If you are using a different shell, just search for the description of its [ or test builtin in its documentation of if it doesn't have such a builtin², in the man page ...

The users on this site kindly helped me determine how to write a bash for loop that iterates over string values. For example, suppose that a loop control variable fname iterates over the strings "a.txt" "b.txt" "c.txt" .

2015年2月12日 · #!/bin/bash ping -c1 10.1.1.23 > /dev/null if [ $? -eq 0 ] then echo ok exit 0 else echo “fail” fi You need to send the output to /dev/null so it won't appear on the screen.-c is meant for count. If you put -c30, you're going to ping 30 times before your script can move on to …

2014年1月30日 · #!/bin/bash # declare associative array with all animals and no value declare -A ANIMALS=(["dog"]= ["cat"]= ["horse"]=) test_animal() { # check if parameter is found within the associative array if [[ -v ANIMALS[$1] ]] ; then echo "$1 is an animal" else echo "$1 is NOT an animal" fi } test_animal "sun" test_animal "tree" test_animal "dog" test ...

2017年10月6日 · bash; variable; test; See similar questions with these tags. The Overflow Blog “The power of the humble ...