如何验证程序是否存在,以返回错误并退出,或继续执行脚本?

看起来应该很容易,但这让我很为难。


当前回答

为了模拟Bash的-P cmd类型,我们可以使用POSIX兼容的env-i type cmd 1>/dev/null 2>&1。

man env
# "The option '-i' causes env to completely ignore the environment it inherits."
# In other words, there are no aliases or functions to be looked up by the type command.

ls() { echo 'Hello, world!'; }

ls
type ls
env -i type ls

cmd=ls
cmd=lsx
env -i type $cmd 1>/dev/null 2>&1 || { echo "$cmd not found"; exit 1; }

其他回答

为了模拟Bash的-P cmd类型,我们可以使用POSIX兼容的env-i type cmd 1>/dev/null 2>&1。

man env
# "The option '-i' causes env to completely ignore the environment it inherits."
# In other words, there are no aliases or functions to be looked up by the type command.

ls() { echo 'Hello, world!'; }

ls
type ls
env -i type ls

cmd=ls
cmd=lsx
env -i type $cmd 1>/dev/null 2>&1 || { echo "$cmd not found"; exit 1; }

尝试使用:

test -x filename

or

[ -x filename ]

从条件表达式下的Bash手册页:

-x文件如果文件存在且可执行,则为True。

我支持使用“命令-v”。例如:

md=$(command -v mkdirhier) ; alias md=${md:=mkdir}  # bash

emacs="$(command -v emacs) -nw" || emacs=nano
alias e=$emacs
[[ -z $(command -v jed) ]] && alias jed=$emacs

这将根据位置判断程序是否存在:

    if [ -x /usr/bin/yum ]; then
        echo "This is Centos"
    fi
checkexists() {
    while [ -n "$1" ]; do
        [ -n "$(which "$1")" ] || echo "$1": command not found
        shift
    done
}