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linux:bash [2016/11/30 08:51] – niziaklinux:bash [2023/11/23 06:57] (current) – niziak
Line 1: Line 1:
 ====== Bash ====== ====== Bash ======
 +
 +===== re-run as other user =====
 +
 +<code bash>
 +if [ $UID == 0 ]; then
 +    exec su -c "$0" john
 +fi
 +</code>
 +
 +===== Check if command is installed =====
 +
 +<code bash>
 +if ! command -v "${TOOL}" &>/dev/null; then
 +    echo " Command ${TOOL} not found. Please install it"
 +    exit 1
 +fi
 +</code>
 +
 +and use it inside loop:
 +<code bash>
 +for tool in awk bc sed; do
 +    ....
 +done
 +</code>
 +
 +===== Output =====
 +
 +<code bash>
 +DEBUG() {
 +    if [ $DEBUG_ENABLE -eq 1 ]; then
 +    >&2 echo "DBG: $@"
 +    fi
 +}
 +</code>
 +
 +===== Variables with space =====
 +
 +<code bash>
 +# Treat arguments as parts of one argument
 +declare DST=$*
 +
 +# Use double colons to pass argument with spaces
 +nice ionice -c idle btrfs filesystem defragment -v -r -czlib "${DST}"
 +</code>
 +
 +Quote problematic characters to use in shell invocation:
 +<code bash>
 +  QUOTED_VAR="${VAR@Q}"
 +</code>
 +
  
 ===== Default values ===== ===== Default values =====
Line 21: Line 71:
 done < <(ls -1 /tmp/) done < <(ls -1 /tmp/)
 </code> </code>
 +
 +==== 'read' insid loop ====
 +In loop where stdin is redirected the easiest way to use read is:
 +<code bash>
 +TTY=`tty`
 +while read ...
 +do
 +  read CTRLC < ${TTY}
 +done < somedata
 +</code>
 +
  
 ===== concatenate output (subshell) ===== ===== concatenate output (subshell) =====
Line 65: Line 126:
  
 <code bash> <code bash>
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && cd -P "$( dirname "$SOURCE" )" && pwd )"+# Works correctly if script is sourced from another one 
 +DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && cd -P "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 </code> </code>
  
 <code bash> <code bash>
 cur_file="${BASH_SOURCE[${#BASH_SOURCE[@]} - 1]}" cur_file="${BASH_SOURCE[${#BASH_SOURCE[@]} - 1]}"
-cur_dir="$(dirname "${cur_file}")+cur_dir="$(dirname "${cur_file}")"
 </code> </code>