-f, --canonicalize canonicalize by following every symlink in every component of the given name recursively; all but the last component must exist
$ readlink -f -- "$(which awk)"/usr/bin/gawk
You can't assign to the positional parameters individually$0 değişkeni - positional parameter
echo $0$0As $0 contains the shell command that is running your shell script or interactive session; when you type $0 in a terminal, you are invoking the command name within the $0 argument variable.
When $0 contains bash; Typing $0 in the terminal, just runs bash. It then runs another bash within the scope of the first one, as a sub-shell.
As it runs another shell, it look like it did nothing, but started another shell session with same environment variables and settings. The shell prompt and current directory are exactly the same, so it look like nothing happened.
If you then try to close the terminal window, while a sub-shell has been invoked, it will tell you there are still background processes running.
What happens when you close the terminal window, is: It signals the first higher level shell Process ID to terminate, but this shell's PID know it has some child PID still attached, and just tells you about it.
qh() {
"$1" --help | grep -- "$2"
}The list of positional parameters can be as long as required and as current resource limits allows. This means that there may be well over 9 elements in the list. As you have already noticed, elements 10 and later may be accessed by adding braces around the number, as in ${12}.
#! /bin/bash
echo $14./file 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
echo ${14}Someone else can probably explain this with much more detail and historical reference but the short answer:/lib
is a place for the essential standard libraries. Think of libraries required for your system to run. If something in /bin or /sbin needs a library that library is likely in /lib.
/usr/lib
the /usr directory in general is as it sounds, a user based directory. Here you will find things used by the users on the system. So if you install an application that needs libraries they might go to /usr/lib. If a binary in /usr/bin or /usr/sbin needs a library it will likely be in /usr/lib.
/var/lib
the /var directory is the writable counterpart to the /usr directory which is often required to be read-only. So /var/lib would have a similar purpose as /usr/lib but with the ability to write to them.
If subscript is @ or *, the word expands to all members of name. These subscripts differ only when the word appears within double quotes. If the word is double-quoted, ${name[*]} expands to a single word with the value of each array member separated by the first character of the IFS special variable, and ${name[@]} expands each element of name to a separate word. When there are no array members, ${name[@]} expands to nothing. If the double-quoted expansion occurs within a word, the expansion of the first parameter is joined with the beginning part of the original word, and the expansion of the last parameter is joined with the last part of the original word.
readarray -t a < pathlist.txt
find "${a[@]}" -type f ....
declare data
data="pig,cow,horse,rattlesnake,"
declare -a my_array
IFS=',' read -r -a my_array <<< "$data"
for item in "${my_array[@]}"; do echo "$item"; donedirs=(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z)
for dir in "${dirs[@]}"
do
mkdir -p $dir
donefor ((i=0 ; i < ${#array[@]} ; i++ )) ; do
echo "${array[i]}"
done#!/bin/bash
array=( "one" "two" "three" "four" "five" )
function get_input() {
read -p "${1}: " number
if [[ " ${array[*]} " == *" ${number} "* ]]
then
echo 'true';
else
get_input 'Try again' # a recursive call of the function
fi
}
get_input 'Enter a number' # the initial call of the functionKind runs a local kubernetes cluster in Docker container and is an effective use to manage local kubernetes cluster deployment. The other alternative for local k8s cluster management is minikube...
kind create cluster --name local-dev
The basic idea of a Kubernetes Operator is to extend the Kubernetes’s level-driven reconciliation loop and API set towards running stateful application workloads natively on Kubernetes. A Kubernetes Operator consists of Kubernetes Custom Resource(s) / API(s) and Kubernetes Custom Controller(s).
An Operator is packaged as a container image and is deployed in a Kubernetes cluster using Kubernetes YAMLs.
The Custom Resources represent an API that takes declarative inputs on the workload being abstracted and the Custom Controller implements corresponding actions on the workload. Kubernetes Operators are typically implemented in a standard programming language (Golang, Python, Java, etc.).
Once deployed, new Custom Resources (e.g. Mysql, Cassandra, etc.) are available to the end users similar to built-in Resources (e.g. Pod, Service, etc.). This allows them to orchestrate their application workflows more effectively leveraging additional Custom Resources.
In order for the Custom Resources to be recognized in a cluster, they need to be first registered in the cluster using Kubernetes’s meta API of ‘Custom Resource Definition (CRD)’. The CRD itself is a Kubernetes resource.
Örnek - Vitess- Register Custom Resource Definitions in Helm chart (and not in Operator code)
- Make sure Custom Resource Definitions are getting installed prior to the Operator deployment
- Define Custom Resource validation rules in CRD YAML
- Use values.yaml or ConfigMaps for Operator configurables
- Add Platform-as-Code annotations to enable easy discovery and consumption of Operator’s Custom Resources
git clone git@github.com:vitessio/vitess.gitcd vitess/examples/operatorkubectl apply -f operator.yaml
Some folders may contain symbolic links that link to another part of your file system. As such, you might unknowingly search a much larger set of folders, if symbolic links do exist. As such, there are a number of options that control what happens when find comes across a symbolic link:
- -P - when used, symbolic links are never followed.
- -L - when used, symbolic links are always followed.
- -H - when used, symbolic links are only followed if mentioned somewhere on the command line, i.e. if you search for a link, and there is a symbolic link called link, find will return a link along with anything found when following that symbolic link.
-P Never follow symbolic links. This is the default behaviour.
When find examines or prints information a file, and the file is
a symbolic link, the information used shall be taken from the
properties of the symbolic link itself.
-L Follow symbolic links. [...]
-H Do not follow symbolic links, except while processing the com‐
mand line arguments. When find examines or prints information
about files, the information used shall be taken from the prop‐
erties of the symbolic link itself. The only exception to this
behaviour is when a file specified on the command line is a sym‐
bolic link, and the link can be resolved. For that situation,
the information used is taken from whatever the link points to
(that is, the link is followed). The information about the link
itself is used as a fallback if the file pointed to by the sym‐
bolic link cannot be examined. If -H is in effect and one of
the paths specified on the command line is a symbolic link to a
directory, the contents of that directory will be examined
(though of course -maxdepth 0 would prevent this).find -H /bin -iname 'sh*'$ find /bin -iname 'sh*'Identify the ID/IDs of your device withxinput listGet the button map withxinput get-button-map <ID>Set the button actionxinput set-button-map <ID> 1 <new action>
Repeat the last command for as many IDs as your mouse has. 1 stands for the mapping of left-click, then for middle click, etc. Use for <new action> number 0 to disable middle-click, number 1 if you want to make it equivalent to left-click, etc.
myhost,1.2.3.4 ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYT...YjdB=
It is permissible (but not recommended) to have several lines or different host keys for the same names.
apiVersion: v1
kind: Pod
metadata:
name: static-web
labels:
role: myrole
spec:
containers:
- name: nginx
image: nginx
envFrom:
- configMapRef:
name: testconfigmapapiVersion: v1kind: ConfigMapmetadata:name: mongodbdata:database-name: microservices
apiVersion: v1 kind: ConfigMap metadata: name: geared-marsupi-configmap data: myvalue: "Hello World" drink: coffee
#Create ConfigMap kubectl create configmap testconfigmap --from-literal=TestKey1=TestValue1
--from-literal=TestKey2=TestValue2 kubectl create configmap testconfigmap --from-file=/opt/test_file #Test kubectl get configmaps kubectl describe configmaps kubectl describe configmap testconfigmap
1. Use the contents of an entire directory with kubectl create configmap my-config --from-file=./my/dir/path/2. Use the contents of a file or specific set of files with kubectl create configmap my-config --from-file=./my/file.txt
Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. ... WHEN is never, always or auto.Varsayılan değer auto olduğu için şöyle yaparız.
grep --color ...Örnek-L, --files-without-matchSuppress normal output; instead print the name of each input file from which no output would normally have been printed. The scanning will stop on the first match.-l, --files-with-matchesSuppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning will stop on the first match.
grep -L 'dog' $(grep -l 'cat' <list of files>)grep -l lists the names of files with matching stringsÖrnek
grep -lRe abc .if grep -q 'release 7\.[56] ' /etc/redhat-release
then ...Burada non-empty kısmı önemli çünkü bazen düzenli ifadeler ile boş string çıktısı gelebiliyor. Açıklaması şöyle-o, --only-matching
Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.
Many regular expressions can match empty text; for example:$ grep -E '.?' <<<""Örnek
outputs a blank line because the empty line matches. However, adding -o results in no output at all:$ grep -Eo '.?' <<<""
because -o ignores empty matches.
Specifying that -o ignores empty matches means the implementers don’t need to decide what to do with zero-length matches, which would otherwise produce rather lengthy (and useless) output in many circumstances.
$ str='25 results [22 valid, 2 invalid, 1 undefined]'
grep -E -o '[0-9]+' <<<"$str"