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.

2016年7月20日 · For short, IFS=$'\n' assign newline \n to variable IFS. $'string' construct is a quoting mechanism which use to decode ANSI C like escape sequences. This syntax comes from ksh93, and was portable to modern shell like bash, zsh, pdksh, busybox sh. This syntax is not defined by POSIX, but was accepted for SUS issue 7.

str=$'Hello World\n=====\n' Single quotes preceded by a $ is a new syntax that allows to insert escape sequences in strings. Also printf builtin allows to save the resulting output to a variable. printf -v str 'Hello World\n=====\n' Both solutions do not require a subshell.

The "branch" command (b) branches to a predefined label in the editing script or to the end of the script if there's no label, while the "next" command (n) reads the next line of input. The "next" command also outputs the current pattern space (usually the line just read) before reading the next line unless output has been suppressed with -n .

2017年6月17日 · q w e r t y u i o p List of arguments: q w e r t y u i o p Name of this script: ./new.sh And the output of $./new.sh q w e r t y u i o will be: q w e r t y u i o List of arguments: q w e r t y u i o Name of this script: ./new.sh Not enough arguments, need 10 to run. Question: What does the -n mean?

2023年10月2日 · Your original example would run script every N+X seconds, where N is 10, and X is however long script takes to run. This example should be much closer to every N seconds. You should expect and prepare for the case where script takes more than N seconds to complete, and thus you may have multiple instances running concurrently.

2018年6月28日 · However, I can't help but notice that your are parsing the variables in the original file several times; first by the first awk script, and then again with the read, and finally a third time with echo+awk. Each of these steps may throw its own set of errors.

2016年12月6日 · I want to write logic in shell script which will retry it to run again after 15 sec upto 5 times based on "status code=FAIL" if it fails due to some issue.

2021年6月16日 · If sed is called from a shell script, you can use printf to construct the sed script. The script below prints out the most common control characters as backslash escapes; add more if desired. The script below prints out the most common control characters as backslash escapes; add more if desired.

2017年6月14日 · ¹ Technically, while test/[is built in virtually all Bourne-like shells, that's not mandated by POSIX and early versions of the Bourne shell didn't have it built-in.