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。
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
以下是检查命令是否存在于$PATH中并可执行的便携式方法:
[ -x "$(command -v foo)" ]
例子:
if ! [ -x "$(command -v git)" ]; then
echo 'Error: git is not installed.' >&2
exit 1
fi
需要进行可执行检查,因为如果$PATH中找不到具有该名称的可执行文件,bash将返回一个不可执行文件。
还请注意,如果$PATH中存在与可执行文件同名的不可执行文件,则dash会返回前者,即使后者会被执行。这是一个bug,违反了POSIX标准。[错误报告][标准]编辑:从破折号0.5.11(Debian 11)开始,这似乎是固定的。
此外,如果要查找的命令已定义为别名,则此操作将失败。
其他回答
我的Debian服务器设置:
当多个包包含相同的名称时,我遇到了问题。
例如apache2。这就是我的解决方案:
function _apt_install() {
apt-get install -y $1 > /dev/null
}
function _apt_install_norecommends() {
apt-get install -y --no-install-recommends $1 > /dev/null
}
function _apt_available() {
if [ `apt-cache search $1 | grep -o "$1" | uniq | wc -l` = "1" ]; then
echo "Package is available : $1"
PACKAGE_INSTALL="1"
else
echo "Package $1 is NOT available for install"
echo "We can not continue without this package..."
echo "Exitting now.."
exit 0
fi
}
function _package_install {
_apt_available $1
if [ "${PACKAGE_INSTALL}" = "1" ]; then
if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
echo "package is already_installed: $1"
else
echo "installing package : $1, please wait.."
_apt_install $1
sleep 0.5
fi
fi
}
function _package_install_no_recommends {
_apt_available $1
if [ "${PACKAGE_INSTALL}" = "1" ]; then
if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
echo "package is already_installed: $1"
else
echo "installing package : $1, please wait.."
_apt_install_norecommends $1
sleep 0.5
fi
fi
}
剧本
#!/bin/bash
# Commands found in the hash table are checked for existence before being
# executed and non-existence forces a normal PATH search.
shopt -s checkhash
function exists() {
local mycomm=$1; shift || return 1
hash $mycomm 2>/dev/null || \
printf "\xe2\x9c\x98 [ABRT]: $mycomm: command does not exist\n"; return 1;
}
readonly -f exists
exists notacmd
exists bash
hash
bash -c 'printf "Fin.\n"'
后果
✘ [ABRT]: notacmd: command does not exist
hits command
0 /usr/bin/bash
Fin.
GIT=/usr/bin/git # STORE THE RELATIVE PATH
# GIT=$(which git) # USE THIS COMMAND TO SEARCH FOR THE RELATIVE PATH
if [[ ! -e $GIT ]]; then # CHECK IF THE FILE EXISTS
echo "PROGRAM DOES NOT EXIST."
exit 1 # EXIT THE PROGRAM IF IT DOES NOT
fi
# DO SOMETHING ...
exit 0 # EXIT THE PROGRAM IF IT DOES
我必须检查Git是否作为部署CI服务器的一部分安装。我最后的Bash脚本如下(Ubuntu服务器):
if ! builtin type -p git &>/dev/null; then
sudo apt-get -y install git-core
fi
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; }