Shulou(Shulou.com)06/03 Report--

It is believed that many inexperienced people are at a loss about whether the shell script in PATH can be used to detect the input option $1. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

Here is an example 001:

#! / bin/sh# inpath-Verifies that a specified program is either valid as is,# or that it can be found in the PATH directory list.in_path () {# Given a command and the PATH, try to find the command. Returns # 0 if found and executable, 1 if not. Note that this temporarily modifies # the IFS (input field separator) but restores it upon completion. Cmd=$1 path=$2 retval=1 oldIFS=$IFS IFS= ":" for directory in $path do if [- x $directory/$cmd]; then retval=0 # if we're here, we found $cmd in $directory fi done IFS=$oldIFS return $retval} checkForCmdInPath () {var=$1 # The variable slicing notation in the following conditional # needs some explanation: ${var#expr} returns everything after # the match for 'expr' in the variable value (if any), and # ${var%expr} returns everything that doesn't match (in this # case, just the very first character. You can also do this in # Bash with ${var:0:1}, and you could use cut too: cut-C1. If ["$var"! = "]; then if [" ${var%$ {var#?}} "=" / "]; then if [!-x $var]; then return 1 fi elif! In_path $var $PATH; then return 2 fi fi} if [$#-ne 1]; then echo "Usage: $0 command" > & 2; exit 1ficheckForCmdInPath "$1" case $? In 0) echo "$1 found in PATH"; 1) echo "$1 not found or not executable"; 2) echo "$1 not found in PATH";; esacexit 0

The purpose of this script is to detect whether the entered option $1 is in PATH.

There are several things to note about this script:

1) it uses function nesting and in_path function nesting in checkForCmdInPath.

2) ${var%$ {var#?}} in the statement if ["${var%$ {var#?}}" = "/"] is the first character that displays the variable, or you can replace it with ${varname:1:1} or $(echo $var | cut-C1).

3) elif! In_path $var $PATH; then means that if the execution result of in_path $var $PATH is not zero, then

Question:

It is found that the input echo, echo_err, / etco_err all return the correct result, but the input / etc/echo_right (there is an execution file but is not in the PATH) returns found in PATH. I think this script still needs to be improved.

After reading the above, do you know whether the shell script in PATH can be used to detect the entered option $1? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.