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

我想说,由于悬挂别名,没有任何可移植和100%可靠的方法。例如:

alias john='ls --color'
alias paul='george -F'
alias george='ls -h'
alias ringo=/

当然,只有最后一个是有问题的(林戈没有冒犯!)。但从command-v的角度来看,它们都是有效的别名。

为了拒绝像ringo这样的悬空命令,我们必须解析shell内置别名命令的输出并递归到它们中(这里命令-v并不优于别名)。没有任何可移植的解决方案,即使是特定于Bash的解决方案也相当乏味。

注意,类似这样的解决方案将无条件拒绝别名ls='ls-F':

test() { command -v $1 | grep -qv alias }

其他回答

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.

检查多个依赖项并向最终用户通知状态

for cmd in latex pandoc; do
  printf '%-10s' "$cmd"
  if hash "$cmd" 2>/dev/null; then
    echo OK
  else
    echo missing
  fi
done

样本输出:

latex     OK
pandoc    missing

将10调整为最大命令长度。这不是自动的,因为我看不到一种非冗长的POSIX方法:如何在Bash中对齐空格分隔表的列?

检查一些apt包是否与dpkg-s一起安装,否则安装。

请参阅:检查是否安装了apt-get包,如果它不在Linux上,则安装它

前面提到过:如何检查Bash脚本中是否存在程序?

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
}

如果您可以:

which programname

...

type -P programname

如果没有任何可用的外部类型命令(在这里是理所当然的),我们可以使用符合POSIX的env-i sh-c“type cmd 1>/dev/null 2>&1”:

# Portable version of Bash's type -P cmd (without output on stdout)
typep() {
   command -p env -i PATH="$PATH" sh -c '
      export LC_ALL=C LANG=C
      cmd="$1"
      cmd="`type "$cmd" 2>/dev/null || { echo "error: command $cmd not found; exiting ..." 1>&2; exit 1; }`"
      [ $? != 0 ] && exit 1
      case "$cmd" in
        *\ /*) exit 0;;
            *) printf "%s\n" "error: $cmd" 1>&2; exit 1;;
      esac
   ' _ "$1" || exit 1
}

# Get your standard $PATH value
#PATH="$(command -p getconf PATH)"
typep ls
typep builtin
typep ls-temp

至少在Mac OS X v10.6.8(雪豹)上,使用Bash 4.2.24(2)命令-vls与移动的/bin/ls温度不匹配。