linux/docs/shells/bash.md

Bash

stdout/stderr (console and logs)

#!/usr/bin/env bash

# Environment overrides
LOG_LEVEL="${LOG_LEVEL:-INFO}" # TRACE, DEBUG, INFO, WARN, ERROR
LOG_INCLUDE_TS=0               # 0 or 1 = include timestamp
LOG_INCLUDE_TYPE=1             # 0 or 1 = include [LEVEL]

# When set to 1, all log messages are sent to stderr instead of splitting
# INFO/DEBUG/TRACE to stdout and WARN/ERROR to stderr. Useful for scripts
# where stdout must remain clean for pipelines, JSON output, or data export.
LOG_ALL_TO_STDERR=0

# Level mapping
declare -A LEVELS=([TRACE]=0 [DEBUG]=1 [INFO]=2 [WARN]=3 [ERROR]=4)

# Helpers
_log_ts()   { [ "$LOG_INCLUDE_TS" = "1" ]   && printf "[%s]" "$(date -Iseconds)"; }
_log_type() { [ "$LOG_INCLUDE_TYPE" = "1" ] && printf "[%s]" "$1"; }
_log_ok()   { [[ ${LEVELS[$1]} -ge ${LEVELS[$LOG_LEVEL]} ]]; }

# Output selector
_log_out() {
  local level="$1"
  shift
  local msg="$*"

  if [ "$LOG_ALL_TO_STDERR" = "1" ]; then
    printf "%s\n" "$msg" >&2
  else
    case "$level" in
      TRACE|DEBUG|INFO) printf "%s\n" "$msg" >&1 ;;
      WARN|ERROR)       printf "%s\n" "$msg" >&2 ;;
    esac
  fi
}

# Log functions
log_trace() { _log_ok TRACE && _log_out TRACE "$(_log_ts)$(_log_type TRACE) $*"; }
log_debug() { _log_ok DEBUG && _log_out DEBUG "$(_log_ts)$(_log_type DEBUG) $*"; }
log_info()  { _log_ok INFO  && _log_out INFO  "$(_log_ts)$(_log_type INFO)  $*"; }
log_warn()  { _log_ok WARN  && _log_out WARN  "$(_log_ts)$(_log_type WARN)  $*"; }
log_error() { _log_ok ERROR && _log_out ERROR "$(_log_ts)$(_log_type ERROR) $*"; }

# Examples
log_trace "trace example"
log_debug "debug example"
log_info  "info example"
log_warn  "warn example"
log_error "error example"
log_error "error example"

arrays

# creates an array variable
ORPHANS=()

# checks length
if [[ ${#ORPHANS[@]} -eq 0 ]]; then
    echo "No orphans found."
else
    echo "orphans:"
    printf "%s\n" "${ORPHANS[@]}"
fi

associative array

an data structure that lets you store key → value pairs

# clean if already been used
unset PV_PATHS
# declare an associative array, an data structure that lets you store key → value pairs
declare -A PV_PATHS
for name in $(kubectl get pv -o jsonpath='{.items[*].metadata.name}'); do
    path=$(kubectl get pv ${name} -o jsonpath='{.spec.local.path}' 2>/dev/null)
    # check if path is no empty
    [[ -n "${path}" ]] && PV_PATHS["${name}"]="${path}"
done
# print only keys
echo
echo "All Keys:"
printf "%s\n" "${!PV_PATHS[@]}"

echo
echo "All Values:"
# print only values
printf "%s\n" "${PV_PATHS[@]}"

echo
echo "Keys|Values:"
# print all
for key in "${!PV_PATHS[@]}"; do
    printf "%s|%s\n" "$key" "${PV_PATHS[$key]}"
done

misc

#!/bin/bash
script_directory="$(dirname "$(readlink -f "$0")")"
#simbolo para comentário
if <condition>; then
<commands>
fi



if test $variavel -eq 3; then
 echo
fi


if [ $variavel -eq 3 ]; then
 echo
fi

if [ ! $variavel -eq 3 ]; then
 echo
fi

if [ $variavel -eq 3 -a $variavel -eq 2 -o $variavel -eq 1]; then
 echo
fi
``





#!/bin/bash

function echoArguments(){
    echo "printing ($#) arguments"
    for ARGUMENT in "$@"
    do
    echo $ARGUMENT
    done
}
echoArguments $@
Também é possível aceder por índice

#!/bin/bash

function echoArguments(){
   echo "$0"
   echo "$1"
}
echoArguments $@
Testar se um programa está a correr
if pgrep jivelite>/dev/null
 then echo "a correr"
 else echo "nao esta correr"
fi
verifica o numero de parametros
cuidado tem que ter mesmo os espaços nos parenteses rectos

if [ "$#" -ne 2 ]
then
 echo "wrong number of parameters($#)"
 echo "0 - name of processo to search" 
 echo "1 - commando to start"
 exit 1
fi
``