shell 脚本和snippets

err() {
    echo "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $@" >&2
}

if ! do_something; then
    err "Unable to do_something"
    exit "${E_DID_NOTHING}"
fi

## Problems: 
## 1.Output line of * is replaced with list of local files
## 2.can't deal with whitespace
arr=( $( curl -k "$url" | jq -r '.[].item2' ) )

## BEST: Supports bash 4.4+, with failure detection and newlines in data
{ readarray -t -d '' arr && wait "$!"; } < <(
  set -o pipefail
  curl --fail -k "$url" | jq -j '.[].item2 | (., "\u0000")'
)

## OK (with bash 4.0), but can't detect failure and doesn't support values with newlines
readarray -t arr < <(curl -k "$url" | jq -r '.[].item2' )

## OK: Supports bash 3.x; no support for newlines in values, but can detect failures
IFS=$'\n' read -r -d '' -a arr < <(
  set -o pipefail
  curl --fail -k "$url" | jq -r '.[].item2' && printf '\0'
)

## OK: Supports bash 3.x and supports newlines in values; does not detect failures
arr=( )
while IFS= read -r -d '' item; do
  arr+=( "$item" )
done < <(curl --fail -k "$url" | jq -j '.[] | (.item2, "\u0000")')

## Set the delimiter using IFS (comma in this case)
IFS="," read -ra my_array <<< "$my_string"
## Set IFS and use array assignment
IFS=',' my_array=($my_string)
## Use tr command to replace the delimiter character with a newline
my_array=($(echo $my_string | tr "," "\n"))

$ command -v java | echo $? 
0
$ command -v go | echo $? 
1

if command -v java >&2; then
## 或者 if type -a java >&2; then
  echo java is available
else
  echo java is not available
fi

## 标准错误的输出重定向到标准输出，&指示不要把1当作普通文件，而是fd=1即标准输出来处理
java -XshowSettings:properties -version 2>&1 | awk -F= '$1~"java.home" {sub(/^[ ]+/, "", $2); print $2}'
## 或者，标准错误的输出重定向到文件
java -XshowSettings:properties -version 2> /tmp/java.properties;cat /tmp/java.properties | grep "java.home" | awk -F'= ' '{print $2}'

branch=$(git branch | sed -n -e 's/^\* \(.*\)/\1/p')
## or
branch=$(git symbolic-ref HEAD | sed -e 's,.*/\(.*\),\1,')

## Ref: https://stackoverflow.com/questions/21151178/shell-script-to-check-if-specified-git-branch-exists
## return 1 if the branch exists in the local, or 0 if not.
function is_in_local() {
    local branch=${1}
    local existed_in_local=$(git branch --list ${branch})

    if [[ -z ${existed_in_local} ]]; then
        echo 0
    else
        echo 1
    fi
}

## Ref: https://stackoverflow.com/questions/8223906/how-to-check-if-remote-branch-exists-on-a-given-remote-repository
## return 1 if its remote branch exists, or 0 if not.
function is_in_remote() {
    local branch=${1}
    local origin=${2}
    local existed_in_remote=$(git ls-remote --heads ${origin} ${branch})

    if [[ -z ${existed_in_remote} ]]; then
        echo 0
    else
        echo 1
    fi
}

alias gitpushall='git remote | xargs -I {} sh -c 'echo "push to: {}"; git push {} --all''

## top 执行一次，并打印 程序列表
top -bn 1 | awk '{ if (NR > 7) print }' 

## numfmt 可以转换带单位的数字。
top -bn 1  | awk '{ if (NR > 7) print }' |awk '{print $6}' |tr 'a-z' 'A-Z' | numfmt --from=auto |awk '{s+=$1} END {print s}' |numfmt --to=si

du -h --max-depth=1  | numfmt --from=auto | sort -n -k 1 |numfmt --to=si 

find ~/.m2/repository/ -atime +30 -iname '*.pom' -print0 | while read -d '' -r pom; do echo rm -rf "$(dirname $pom)"; done 

## mac
uname | grep Darwin -q && option_for_mac="-ptcp"    
netstat -tna ${option_for_mac:-} | awk 'NR>=3 {++State[$6]} END {for (key in State) print key,State[key]}'
#linux
netstat -ant|awk '/^tcp/ {++S[$NF]} END {for(a in S) print (a,S[a])}'

## linux
netstat -ant | awk '{print $5}' | awk -F: '{print $1}' | grep -E "^[0-9]" | sort | uniq -c | sort -nr