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envrc-rs's Introduction

envrc - Auto source bash .envrc of your workspace

Wny?

Firstly, direnv doesn't officially support alias at the moment.

Secondly,

direnv is actually creating a new bash process to load the stdlib, direnvrc and .envrc, and only exports the environment diff back to the original shell.

However, envrc is simpler. It spawns a new interactive bash and load .envrc. When you cd out of the directory, the shell exits and returns terminal back to the original shell.

Install

  • cargo install envrc
  • Add PROMPT_COMMAND='eval "$(envrc bash)"' to the end of your bashrc

Usage

$ mkdir foo
$ 
$ echo 'echo in foo directory' > foo/.envrc
$ 
$ cd foo
  envrc: spawning new /bin/bash
  envrc: loading [/home/roxma/test/envrc/foo/.envrc]
  in foo directory
$ 
$ cd ..
  envrc: exit [/home/roxma/test/envrc/foo/.envrc]
$ envrc
  envrc 0.2
  Rox Ma [email protected]
  auto source .envrc of your workspace

  USAGE:
      envrc [SUBCOMMAND]

  FLAGS:
      -h, --help       Prints help information
      -V, --version    Prints version information

  SUBCOMMANDS:
      allow    Grant permission to envrc to load the .envrc
      bash     for bashrc: PROMPT_COMMAND='eval "$(envrc bash)"'
      deny     Remove the permission
      help     Prints this message or the help of the given subcommand(s)
      prune    Remove expired or non-existing-file permissions

Note: Take care of your background jobs before getting out of .envrc.

.envrc tips

  • export WORKSPACE_DIR=$(readlink -f "$(dirname "${BASH_SOURCE[0]}")") for .envrc to locate its directory.
  • exec bash to reload the modifed .envrc

.bashrc config

# If the `.envrc` is allowed, but not sourced for 1d since last unload, It
# will be considered expired
export ENVRC_ALLOW_DURATION=$((60*60*24))
PROMPT_COMMAND='eval "$(envrc bash)"'

Why not bash/python?

The first working commit is written in python. But there's noticeable time lag with the python version on my PC. Rewriting it with perl doesn't help either. Then I decided to switch to rust.

$ time envrc.py bash-prompt-command >/dev/null
real    0m0.079s
user    0m0.044s
sys     0m0.004s

I have also tried a pure bash implementation. It works better than the python implementation, since most of the python overhead is its startup time. Most of the bash overhead is fork/exec of sub-processes and it's way slower than the rust implementation. Read #1 for more information.

envrc-rs's People

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envrc-rs's Issues

Pure bash implementation seems to be fast enough too?

#!/bin/bash
PROMPT_COMMAND=envrc_prompt_command

function envrc_find() {
    local d="$PWD"

    while :
    do
        if [ -f "$d/.envrc" ]
        then
            echo "$d/.envrc"
        fi

        if [ "$d" == "/" -o "$d" == "." ]
        then
            return
        fi

        d="$(exec dirname "$d")"
    done
}

function envrc_prompt_command() {
    local rc_found="$(envrc_find)"

    if [ "$rc_found" == "$ENVRC_LOAD" ]
    then
        if [ -n "$ENVRC_LOAD" -a -z "$ENVRC_LOADED" -a "$ENVRC_PPID" == "$PPID" ]
        then
            ENVRC_LOADED=1
            . "$ENVRC_LOAD"
        elif [ -n "$ENVRC_LOAD" -a "$ENVRC_PPID" != "$PPID" ]
        then
            unset ENVRC_LOAD
            unset ENVRC_LOADED
            unset ENVRC_PPID
            unset ENVRC_TMP
            envrc_prompt_command
        fi
        return
    fi

    if [ "$ENVRC_LOAD" == "" ]
    then
        local tmp="$(mktemp --suffix=_envrc)"
        if [ -z "$tmp" ]
        then
            return
        fi
        echo "exit 0" > "$tmp"

        echo "envrc: spawn for [$rc_found]"
        ENVRC_TMP="$tmp" ENVRC_LOAD="$rc_found" ENVRC_PPID=$$ $BASH
        eval "$(cat "$tmp"; rm "$tmp")"
        envrc_prompt_command
    else
        echo "cd '$PWD'
        export OLDPWD='$OLDPWD'" > $ENVRC_TMP
        echo "envrc: exit [$ENVRC_LOAD]"
        exit 0
    fi
}
$ time envrc_prompt_command 

real    0m0.010s
user    0m0.000s
sys     0m0.000s

Most of the time is spent on bash's forking child processes and sub shells. The directory gets deeper, it takes longer. When the directory gets deep enough, the time lag starts to get annoying.

The rust implementation always takes about 0.002 seconds (overhead of system exec-fork).

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