Est-ce que bash a un hook qui est lancé avant l'exécution d'une commande ?

Vous pouvez utiliser le trap (de help trap ) :

Si un SIGNAL_SPEC est DEBUG, ARG est exécuté avant chaque commande simple.

Par exemple, pour changer le titre du terminal de façon dynamique, vous pouvez utiliser :

trap 'echo -ne "\e]0;$BASH_COMMAND\007"' DEBUG

から こん source.

Ce n'est pas une fonction Shell qui est exécutée, mais j'ai contribué à la création d'une fonction $PS0 Chaîne d'invite qui s'affiche avant l'exécution de chaque commande. Détails ici : http://stromberg.dnsalias.org/~strombrg/PS0-prompt/

$PS0 est inclus dans bash 4.4, bien qu'il faille un certain temps pour que la plupart des Linux intègrent la 4.4 - vous pouvez cependant compiler la 4.4 vous-même si vous le souhaitez ; dans ce cas, vous devriez probablement le mettre sous /usr/local et l'ajouter à /etc/shells et chsh à celui-ci. Puis déconnectez-vous et reconnectez-vous, peut-être ssh à vous-même@localhost ou su d'abord à vous-même comme un test.

J'ai récemment dû résoudre ce problème exact pour un de mes projets secondaires. J'ai créé une solution assez robuste et résiliente qui émule les fonctionnalités preexec et precmd de zsh pour bash.

https://github.com/rcaloras/bash-preexec

Il était à l'origine basé sur la solution de Glyph Lefkowitz, mais je l'ai amélioré et mis à jour. Heureux d'aider ou d'ajouter une fonctionnalité si nécessaire.

Merci pour les conseils ! J'ai fini par utiliser ceci :

#created by francois scheurer

#sourced by '~/.bashrc', which is the last runned startup script for bash invocation
#for login interactive, login non-interactive and non-login interactive shells.
#note that a user can easily avoid calling this file by using options like '--norc';
#he also can unset or overwrite variables like 'PROMPT_COMMAND'.
#therefore it is useful for audit but not for security.

#prompt & color
#http://www.pixelbeat.org/docs/terminal_colours/#256
#http://www.frexx.de/xterm-256-notes/
_backnone="\e[00m"
_backblack="\e[40m"
_backblue="\e[44m"
_frontred_b="\e[01;31m"
_frontgreen_b="\e[01;32m"
_frontgrey_b="\e[01;37m"
_frontgrey="\e[00;37m"
_frontblue_b="\e[01;34m"
PS1="\[${_backblue}${_frontgreen_b}\]\u@\h:\[${_backblack}${_frontblue_b}\]\w\\$\[${_backnone}${_frontgreen_b}\] "

#'history' options
declare -rx HISTFILE="$HOME/.bash_history"
chattr +a "$HISTFILE" # set append-only
declare -rx HISTSIZE=500000 #nbr of cmds in memory
declare -rx HISTFILESIZE=500000 #nbr of cmds on file
declare -rx HISTCONTROL="" #does not ignore spaces or duplicates
declare -rx HISTIGNORE="" #does not ignore patterns
declare -rx HISTCMD #history line number
history -r #to reload history from file if a prior HISTSIZE has truncated it
if groups | grep -q root; then declare -x TMOUT=3600; fi #timeout for root's sessions

#enable forward search (ctrl-s)
#http://ruslanspivak.com/2010/11/25/bash-history-incremental-search-forward/
stty -ixon

#history substitution ask for a confirmation
shopt -s histverify

#add timestamps in history - obsoleted with logger/syslog
#http://www.thegeekstuff.com/2008/08/15-examples-to-master-linux-command-line-history/#more-130
#declare -rx HISTTIMEFORMAT='%F %T '

#bash audit & traceabilty
#
#
declare -rx AUDIT_LOGINUSER="$(who -mu | awk '{print $1}')"
declare -rx AUDIT_LOGINPID="$(who -mu | awk '{print $6}')"
declare -rx AUDIT_USER="$USER" #defined by pam during su/sudo
declare -rx AUDIT_PID="$$"
declare -rx AUDIT_TTY="$(who -mu | awk '{print $2}')"
declare -rx AUDIT_SSH="$([ -n "$SSH_CONNECTION" ] && echo "$SSH_CONNECTION" | awk '{print $1":"$2"->"$3":"$4}')"
declare -rx AUDIT_STR="[audit $AUDIT_LOGINUSER/$AUDIT_LOGINPID as $AUDIT_USER/$AUDIT_PID on $AUDIT_TTY/$AUDIT_SSH]"
declare -rx AUDIT_SYSLOG="1" #to use a local syslogd
#
#PROMPT_COMMAND solution is working but the syslog message are sent *after* the command execution, 
#this causes 'su' or 'sudo' commands to appear only after logouts, and 'cd' commands to display wrong working directory
#http://jablonskis.org/2011/howto-log-bash-history-to-syslog/
#declare -rx PROMPT_COMMAND='history -a >(tee -a ~/.bash_history | logger -p user.info -t "$AUDIT_STR $PWD")' #avoid subshells here or duplicate execution will occurs!
#
#another solution is to use 'trap' DEBUG, which is executed *before* the command.
#http://superuser.com/questions/175799/does-bash-have-a-hook-that-is-run-before-executing-a-command
#http://www.davidpashley.com/articles/xterm-titles-with-bash.html
#set -o functrace; trap 'echo -ne "===$BASH_COMMAND===${_backvoid}${_frontgrey}\n"' DEBUG
set +o functrace #disable trap DEBUG inherited in functions, command substitutions or subshells, normally the default setting already
#enable extended pattern matching operators
shopt -s extglob
#function audit_DEBUG() {
#  echo -ne "${_backnone}${_frontgrey}"
#  (history -a >(logger -p user.info -t "$AUDIT_STR $PWD" < <(tee -a ~/.bash_history))) && sync && history -c && history -r
#  #http://stackoverflow.com/questions/103944/real-time-history-export-amongst-bash-terminal-windows
#  #'history -c && history -r' force a refresh of the history because 'history -a' was called within a subshell and therefore
#  #the new history commands that are appent to file will keep their "new" status outside of the subshell, causing their logging
#  #to re-occur on every function call...
#  #note that without the subshell, piped bash commands would hang... (it seems that the trap + process substitution interfer with stdin redirection)
#  #and with the subshell
#}
##enable trap DEBUG inherited for all subsequent functions; required to audit commands beginning with the char '(' for a subshell
#set -o functrace #=> problem: completion in commands avoid logging them
function audit_DEBUG() {
    #simplier and quicker version! avoid 'sync' and 'history -r' that are time consuming!
    if [ "$BASH_COMMAND" != "$PROMPT_COMMAND" ] #avoid logging unexecuted commands after Ctrl-C or Empty+Enter
    then
        echo -ne "${_backnone}${_frontgrey}"
        local AUDIT_CMD="$(history 1)" #current history command
        #remove in last history cmd its line number (if any) and send to syslog
        if [ -n "$AUDIT_SYSLOG" ]
        then
            if ! logger -p user.info -t "$AUDIT_STR $PWD" "${AUDIT_CMD##*( )?(+([0-9])[^0-9])*( )}"
            then
                echo error "$AUDIT_STR $PWD" "${AUDIT_CMD##*( )?(+([0-9])[^0-9])*( )}"
            fi
        else
            echo $( date +%F_%H:%M:%S ) "$AUDIT_STR $PWD" "${AUDIT_CMD##*( )?(+([0-9])[^0-9])*( )}" >>/var/log/userlog.info
        fi
    fi
    #echo "===cmd:$BASH_COMMAND/subshell:$BASH_SUBSHELL/fc:$(fc -l -1)/history:$(history 1)/histline:${AUDIT_CMD%%+([^ 0-9])*}===" #for debugging
}
function audit_EXIT() {
    local AUDIT_STATUS="$?"
    if [ -n "$AUDIT_SYSLOG" ]
    then
        logger -p user.info -t "$AUDIT_STR" "#=== bash session ended. ==="
    else
        echo $( date +%F_%H:%M:%S ) "$AUDIT_STR" "#=== bash session ended. ===" >>/var/log/userlog.info
    fi
    exit "$AUDIT_STATUS"
}
#make audit trap functions readonly; disable trap DEBUG inherited (normally the default setting already)
declare -fr +t audit_DEBUG
declare -fr +t audit_EXIT
if [ -n "$AUDIT_SYSLOG" ]
then
    logger -p user.info -t "$AUDIT_STR" "#=== New bash session started. ===" #audit the session openning
else
    echo $( date +%F_%H:%M:%S ) "$AUDIT_STR" "#=== New bash session started. ===" >>/var/log/userlog.info
fi
#when a bash command is executed it launches first the audit_DEBUG(),
#then the trap DEBUG is disabled to avoid a useless rerun of audit_DEBUG() during the execution of pipes-commands;
#at the end, when the prompt is displayed, re-enable the trap DEBUG
declare -rx PROMPT_COMMAND="trap 'audit_DEBUG; trap DEBUG' DEBUG"
declare -rx BASH_COMMAND #current command executed by user or a trap
declare -rx SHELLOPT #shell options, like functrace  
trap audit_EXIT EXIT #audit the session closing

Profitez-en !