bash script syntax to compare strings as integers

问题:

I have a bash script I am trying to run through directories to the end of the line, for example if I have 4 directories in a row it will go down /d1/d2/d3/d4 until it finds files or other directories. If d3 has a file, it will stop there. I was doing this by counting the lines ls prints to a file and if there's 1 directory use that name in a cd command. My file is:

`

#!/bin/bash


COUNTFILE="/home/username/fake.txt"

ITEMCOUNT=$(ls | wc -l)
echo "ITEMCOUNT" $ITEMCOUNT

echo $*

ONE="1"
echo "one" $ONE

if [["$ITEMCOUNT" -eq "$ONE"]]; 
then
  DIRCOUNT=$(find . -maxdepth 1 -type d | wc -l)
  echo "dircount" $DIRCOUNT
else
  DIRCOUNT="0"
fi


if [$DIRCOUNT == "1"]; then
  ls > $COUNTFILE
  PATH=$(head -1 $COUNTFILE)
  cd ./$PATH
fi

`

As is I get

pipetester.sh: line 15: [[1: command not found
pipetester.sh: line 2

4: [0: command not found

I checked syntax for 2 hours, but it seems to be complaining about my "if" lines, why?

回答1:

Put spaces around command names like [[ and [.

For example:

if [[ "$ITEMCOUNT" -eq "$ONE" ]]
then

or, if you like semicolons:

if [[ "$ITEMCOUNT" -eq "$ONE" ]]; then

And:

if [ $DIRCOUNT == "1" ]; then

or (better use of quotes):

if [ "$DIRCOUNT" == "1" ]; then  # Or just 1 (no quotes around it)

Because these are commands, you need spaces around the components of the expression too (as you have them already). Don't skimp on spaces in shell scripts (but also don't use them where they are not allowed, such as around the = in a variable assignment).

Note that both the [[ command and the == operator for [ are Bash extensions compared to the POSIX shell.

回答2:

You need to put spaces around the [[ and ]] tokens, [[ is an actual command:

if [[ "$ITEMCOUNT" -eq "$ONE" ]];

The way you have it now is little different to expecting ls-al (without a space preceding the -) to give you a full directory listing.

The complaint about the [[1 command is because $ITEMCOUNT is set to 1 and is being combined with the [[ text:

pax$ xyzzy=1

pax$ if [[$xyzzy == 1]]; then echo yes; fi
-bash: [[1: command not found

pax$ if [[ $xyzzy == 1 ]]; then echo yes; fi
yes

You also need to do this for [ and ] as well, for the same reason.