I'm trying to write a script that will only accept exactly one argument. I'm still learning so I don't understand what's wrong with my code. I don't understand why, even though I change the number of inputs the code just exits. (Note: I'm going to use $dir for later if then statements but I haven't included it.)
#!/bin/bash
echo -n "Specify the name of the directory"
read dir
if [ $# -ne 1 ]; then
echo "Script requires one and only one argument"
exit
fi
You can use https://www.shellcheck.net/ to double check your syntax.
$# tells you how many arguments the script was called with.
Here you have two options.
Option 1: Use arguments
#!/bin/bash
if [[ $# -ne 1 ]]
then
echo "Script requires one and only one argument"
exit 1
else
echo "ok, arg1 is $1"
fi
To call the script do: ./script.bash argument
Use [[ ]] for testing conditions (http://mywiki.wooledge.org/BashFAQ/031)
exit 1: by default when a script exists with a 0 status code, it means it worked ok. Here since it is an error, specify a non-zero value.
Option 2: Do not use arguments, ask the user for a value.
Note: this version does not use arguments at all.
#!/bin/bash
read -r -p "Specify the name of the directory: " dir
if [[ ! -d "$dir" ]]
then
echo "Error, directory $dir does not exist."
exit 1
else
echo "ok, directory $dir exists."
fi
To call the script do: ./script.bash without any arguments.
You should research bash tutorials to learn how to use arguments.
Related
On MacOS Catalina, I have a bash script with
if [[ ! -f $CR/home/files/Recovery_*.txt ]]
then
echo "File does not exists in /home/files directory. Exiting" >> $log
echo "Aborted - $CR/home/files/Recovery_*txt not exist"
exit
fi
Even though there are 2 files in the directory the script exits. If I list directory contents beforehand there are 2 files. If I change it as follows the if is skipped:
if [[ `ls -la $CR/home/files/Recovery_*.txt | wc -l` -eq 0 ]]
then
echo "No files are :"
exit
fi
I am wanting to use the if -f conditional.
Any suggestions please?
Cheers, C
If you use nullglob, a glob expression that doesn't match returns an empty string. This lets us count files in bash without spawning other processes. Create an array with the expression, then check its length.
shopt -s nullglob
files=($CR/home/files/Recovery_*.txt)
if [[ ${#files[#]} -eq 0 ]]
then
echo "No files"
exit
fi
[Edited]
The error was not the variables, but the missing shebang as the script has come across from W2K3 SFU.
The tip about shellchecker.net was awesome and I will use that from now.
Thanks.
I want to create a directory with increasing numbers every time I run the script. My current solution is:
COUNTER=1
while mkdir $COUNTER; (( $? != 0 ))
do
COUNTER=$((COUNTER + 1))
done
Is separating the commands in the while condition with a ;(semicolon) the best practice?
The very purpose of while and the shell's other control statements is to run a command and examine its exit code. You can use ! to negate the exit code.
while ! mkdir "$COUNTER"
do
COUNTER=$((COUNTER + 1))
done
Notice also the quoting; see further Why is testing "$?" to see if a command succeeded or not, an anti-pattern?
As such, if you want two commands to run and only care about the exit code from the second, a semicolon is the correct separator. Often, you want both commands to succeed; then, && is the correct separator to use.
You don't need to test the exit status, just check if the directory exists already and increment. Here is one way
#!/usr/bin/env bash
counter=1
while [[ -e $counter ]]; do
((counter++))
done
if ! mkdir "$counter"; then ##: mkdir failed
echo failed ##: execute this code
fi
POSIX sh shell.
#!/usr/bin/env sh
counter=1
while [ -e "$counter" ]; do
counter=$((counter+1))
done
if ! mkdir "$counter"; then ##: If mkdir failed
echo failed ##: Execute this code
fi
The bang ! negates the exit status of mkdir.
See help test | grep '^[[:blank:]]*!'
Well if you're just going to negate the exit status of mkdir inside the while loop then you might as well use until, which is the opposite of while
counter=1
until mkdir "$COUNTER"; do
:
COUNTER=$((COUNTER + 1))
done
I haven't found anything to deal with this particular situation. Maybe there is a easy way that I'm overlooking instead of checking for a string to catch this scenario. When I check an input for existence of a file, if the input is ~/filecheck , this won't work. I get negative results while the file is in my home folder. Any suggestions for improvement to any part of the script I will definitely appreciate. I also have to use an input instead of a argument. Thanks for any help.
my test script
read -p "Enter: " input
echo $input
if [ -f $input ]; then
read -p "Do you REALLY want to delete this file?:" input2
if [[ $input2='y' || $input2 = 'Y' ]]
then
rm -f $input
elif [[ $input2='n' || $input2='N' ]]
then
exit
else
echo "Invaild Option"
exit
fi
else
echo Invaild Option!
exit
fi
Since you are entering input string as ~/filecheck shell doesn't expand tilde while using condition with -f in [ -f $input ]
You can use it this way but it is not recommended and potentially dangerous as arbitrary commands can be run by user:
if [[ -f $(bash -c "echo $input") ]]; then
echo "file exists"
fi
EDIT: As per the comments below to avoid risky bash -c you can use:
if [[ -f "${input/\~/$HOME}" ]]; then
echo "file exists"
fi
You can't have tilde expansion in this part of the program without using something based on eval—and you don't want to do that with user input. So, your poor-man solution will be to substitute any potential leading ~/ with the expansion of $HOME/. Here's the adaptation of your script in an arguably better style:
#!/bin/bash
read -e -p "Enter: " input
input=${input/#~\//$HOME/} # <--- this is the main idea of this answer (and it's rather poor)
echo "$input"
if [[ -f $input ]]; then
read -e -p "Do you REALLY want to delete this file? " input2
if [[ ${input2,,} = y ]]; then
rm -f -- "$input"
elif [[ ${input2,,} = n ]]; then
exit
else
echo "Invalid Option"
exit
fi
else
echo "Invalid Option!"
fi
exit
Now, out of curiosity, why are you spending time to make a wrapper around rm? you're making a clunky interface to an already existing program, without adding anything to it, only rendering it less powerful and less easy to use.
If all what you want it's to ask the user before deleting, you can use:
rm -i
This will give you appropriate error in the case file does not exist.
I'm trying to compile a script that will read user input, and check if the file after the y/n statement. Then it will make files executable. I think the problem with my script is conditional ordering but check it out yourself:
target=/home/user/bin/
cd $target
read -p "This will make the command executable. Are you sure? (y/n)" CONT
if [ "$CONT" == "y" ];
then
chmod +x $1
echo "File $1 is now executable."
else
if [ "$(ls -A /home/user/bin/)" ];
then
echo "File not found."
else
echo "Terminating..."
fi
fi
As I said, I need the script to scan for the file after the y/n statement is printed. The script works fine how it is but still gives the "file is now executable" even if the argument file doesn't exist (but just gives the standard system "cannot find file" message after the echo'd text).
Your script is mostly correct, you just need to check if the file exists first. Also, it's not the best practice to use cd in shell scripts and not needed here.
So re-writing it
#!/bin/bash
target="/home/user/bin/$1"
if [[ ! -f $target ]]; then
echo "File not found."
else
read -p "This will make the command executable. Are you sure? (y/n) " CONT
if [[ $CONT == "y" ]]; then
chmod +x "$target"
echo "File $1 is now executable."
else
echo "Terminating..."
fi
fi
To get an understanding:
Your script will take one argument (a name of a file).
You ask if you want to make that file executable.
If the answer is 'yes', you make the file executable.
Otherwise, you don't.
You want to verify that the file exists too?
I'm trying to understand your logic. What does this:
if [ "$(ls -A /home/user/bin/)" ];
suppose to do. The [ ... ] syntax is a test. And, it has to be one of the valid tests you see here. For example, There's a test:
-e file: True if file exists.
That mean, I can see if your file is under /home/user/bin:
target="/home/user/bin"
if [ -e "$target/$file" ] # The "-e" test for existence
then
echo "Hey! $file exists in the $target directory. I can make it executable."
else
echo "Sorry, $file is not in the $target directory. Can't touch it."
fi
Your $(ls -A /home/user/bin/) will produce a file listing. It's not a valid test like -e unless it just so happens that the first file in your listing is something like -e or -d.
Try to clarify what you want to do. I think this is something more along the lines you want:
#! /bin/bash
target="/home/user/bin"
if [ -z "$1" ] # Did the user give you a parameter
then
echo "No file name given"
exit 2
fi
# File given, see if it exists in $target directory
if [ ! -e "$target/$1" ]
then
echo "File '$target/$1' does not exist."
exit 2
fi
# File was given and exists in the $target directory
read -p"Do you want $target/$1 to be executable? (y/n)" continue
if [ "y" = "$continue" ]
then
chmod +x "$target/$1"
fi
Note how I'm using the testing, and if the testing fails, I simply exit the program. This way, I don't have to keep embedding if/then statements in if/then statements.
I'm writing a reasonably lengthy script (or what I would consider lengthy - you could probably do it in a few hours). I basically have a file (named .restore.info) which contains files of names. In part of the script, I want to test "If cannot find filename in .restore.info, then says “Error: restored file does not exist”. Apologies if this doesn't make sense for you guys (for me, it does in the grand scheme of things). So if type this in the command line:
sh MYSCRIPT filename
It will search for the string filename in the .restore.info file, and if it cant find anything, it should produce an error message.
Basically, I need the top line of this coded translated into a UNIX bash statement and something that actually makes sense!:
If grep $1 .restore.info returns an exist status of 1; then
echo “Filename does not exist!”
fi
Thanks in advance! Please ask me if you need me to clarify anything more clearly as I know I'm not the best explainer, and I'll get back to you in less than a minute! (+rep and best answer of course will be given!)
You probably only care if grep exits with a non-zero exit status:
if ! grep -q "$1" .restore.info; then
echo "Filename does not exist!"
fi
but if you really do care about a specific exit status (1, in this case):
if ! grep -q "$1" .restore.info && [[ $? -eq 1 ]]; then
echo "Filename does not exist!"
fi
Use grep -q
grep -q "filename" .restore.info && echo "found match"
or
! grep -q "filename" .restore.info && echo "not found"
grep -l 'filename' .restore.info
if [ $? = 0 ];then
echo "found it"
else
echo "not found"
fi