如何在bash shell中编写一个优雅的linux命令

Question

I'm running several web applications in my VM which is on Ubuntu 12.04.

I find myself typing the following very often when I ssh into my VM.

• cd /var/virtual/app1.com/
• cd /var/virtual/app2.com/
• cd /var/virtual/app3.com/

Each line represents a separate webapp root directory for me to perform certain instructions.

This is the lazy programmer asking if there is a way for me to type.

• go_app1
• go_app2
• go_app3

I know how to do the above using bash script.

but I will end up typing

./GoApp.sh -app app1

I want to make it more elegant by simply typing go_app1.

Advice?

EDIT:

I used the top-rated answer and I got this error message in Ubuntu.

https://gist.github.com/simkimsia/7336019

Where did I go wrong?

EDIT2:

I have rewritten the error into another question here at command not found message when I try to add command in .bashrc .

Answer 1

Defining an alias for each will certainly work. But since you have multiple desired shortcuts following a pattern, consider a function.

function go_app() { cd /var/virtual/app$1.com/; }

Usage:

go_app 1

Put the function definition in ~/.bashrc.

Answer 2

You could use an alias by placing the below in your .bash_profile.

alias go_app1='cd /var/virtual/app1.com/'

After doing that, typing go_app1 should change your directory.

Answer 3

Would a search through the bash command-history be a good enough solution? I also often have to log into long directory structures, but I usually Ctrl-R through. Eg, if I had fairly recently cd-ed into your app1.com, I'd press Ctrl-R then type app1.com and the last command using app1.com would appear, at which point you press enter and you're done. If "cd" is not the one, you press Ctrl-R a few more times until it appears.

A bit more detail: http://www.catonmat.net/blog/the-definitive-guide-to-bash-command-line-history/

Of course, this works only if you're concerned with how much you type, not if you're trying to do this programmatically, and only if the "cd" command was fairly recent in the list of commands that had "app1.com" (or any other short distinguishing pattern) explicitly.

Answer 4

I would set the $CDPATH variable (in bash ) to all the directories to be searched, including the current directory (at first), like:

 export CDPATH=.:/var/virtual:<other-dirs>

then I can just say:

 cd app1.com

given that, the directory names are short and I can type (rather than search them through the history)

Answer 5

Improving on the corkin alias advice, but given flexibility of "naming" (with argument app1.com, app2.com, ...), this solution solves it with a single alias:

alias go_app='cd /var/virtual/; cd '

afterwards,

go_app app1.com

will cd into /var/virtual/app1.com/ . On naming: I would name it cd_app . On a side note go_app without arguments will kick you back to your home (because the last command is cd without further arguments).

Answer 6

Add this in your .bashrc :

_make_go_apps() {
    local r=/var/virtual
    local d qd
    while read d; do
        printf -v qd '%q' "$r/$d"
        eval "go_${d%.com}() { cd -- $qd; }"
    done < <( find "$r" -maxdepth 1 -regex ".*/app[0-9]+\.com" -type d -printf '%f\n')
}

This will create functions go_appX with X a number such that the directory /var/virtual/appX.com exists, and this function, when called, will just cd into that directory.

Look (don't worry, I'm in a sandbox):

# mkdir -p /var/virtual/app{1..50}.com
# _make_go_apps
# go_app42
# pwd
/var/virtual/app42

Done!

If new directories are created, then just relaunch the function _make_go_apps .

This methods fulfills all the OP's requirements and is general enough to be able to cope with any number of directories.

eval is evil, but used in a safe way (read with sanitized variables, even though it's useless here; but if one day you want to generalize this method, you'll at least have this part correct).

Do not try to generalize this method unless you absolutely know what you're doing: taking care of file names containing spaces, newlines, trailing newlines, etc.

Remarks.

• If you want to change the location /var/virtual , just change the local variable r , making sure it's an absolute path.
• Tab completion of course works very well (and tab-tab will show you the possibilities).

• If you delete some directories, you might want a _clean_go_apps to only retain the relevant go_appX . One possibility is (it'll go in your .bashrc ):

   clean_go_apps() { local r=/var/virtual local f while read _ _ f; do [[ $f =~ ^go_app[[:digit:]]+$ ]] || continue [[ -d $r/${f#go_}.com ]] && continue unset -f $f done < <(declare -F) } 

  In this case, read the next part.

---

Then you'll realize it's not a good idea to have /var/virtual in two distinct places, so you'll want to use a global variable, and you'll end up with this in your .bashrc :

readonly _go_apps_basedir=/var/virtual
make_go_apps() {
    local d qd
    while IFS= read -d '' d; do
        printf -v qd '%q' "$_go_apps_basedir/$d"
        eval "go_${d%.com}() { cd -- $qd; }"
    done < <( find "$_go_apps_basedir" -maxdepth 1 -regex ".*/app[0-9]+\.com" -type d -printf '%f\0')
}

clean_go_apps() {
    local f
    while read _ _ f; do
        [[ $f =~ ^go_app[[:digit:]]+$ ]] || continue
        [[ -d "$_go_apps_basedir/${f#go_}.com" ]] && continue
        unset -f $f
    done < <(declare -F)
}

make_go_apps

I marked the variable _go_apps_basedir readonly , so that it's not changed inadvertently. This time I chose to use IFS='' and -d '' in the read, together with -printf '%f\\0' in the find command, to show you how to do safe stuff when parsing the output of find .

---

I'm still concerned about the find in the _make_go_apps function, as it's not a 100% pure bash solution. Here's a 100% pure bash solution:

readonly _go_apps_basedir=/var/virtual
make_go_apps() {
    local f d qd saved_shopt
    saved_shopt=$(shopt -p)
    shopt -s extglob nullglob
    for d in "$_go_apps_basedir"/app+([[:digit:]]).com/; do
        f=${d#$_go_apps_basedir/}
        printf -v qd '%q' "$d"
        eval "go_${f%.com/}() { cd -- $qd; }"
    done
    eval "$saved_shopt"
}

clean_go_apps() {
    local f
    while read _ _ f; do
        [[ $f =~ ^go_app[[:digit:]]+$ ]] || continue
        [[ -d "$_go_apps_basedir/${f#go_}.com" ]] && continue
        unset -f $f
    done < <(declare -F)
}

make_go_apps

---

Sorry for this long an messy post... I was more or less thinking while typing (not good to do!), and I never wanted to erase the previous parts, as they contain interesting stuff.

---

Edit . Now, to make this post even longer, here's the same, but that will create a go_X function for every directory X.com inside /var/virtual , such that X only contains the characters: [0-9a-zA-Z\\-\\._] . Put this in your .bashrc :

readonly _go_apps_basedir=/var/virtual
make_go_functions() {
    local f d qd saved_shopt
    saved_shopt=$(shopt -p)
    shopt -s extglob nullglob
    for d in "$_go_apps_basedir"/+([[:alpha:][:digit:]\-\._]).com/; do
        f=${d#$_go_apps_basedir/}
        printf -v qd '%q' "$d"
        eval "go_${f%.com/}() { cd -- $qd; }"
    done
    eval "$saved_shopt"
}

clean_go_apps() {
    local f
    while read _ _ f; do
        [[ $f =~ ^go_.+$ ]] || continue
        [[ -d "$_go_apps_basedir/${f#go_}.com" ]] && continue
        unset -f $f
    done < <(declare -F)
}

make_go_functions