Simple bash shell program - bash

I want to write the bash script which would accept 4 parameters: name of file, name of directory, and two strings.
If there is a mistake (if first parameter is not a file or second is not a directory) then string which is a third parameter should be printed else file should be copied to directory and string which is a fourth parameter should be printed. I don't why the compiler reports mistake in line 3 with then.
#!/bin/bash
if [-f $1]; then
if[-d $2] ; then
cp $1 / $2
echo $4
fi
done
else
echo $3
exit 1
fi

If you are having problems, paste your code in at https://www.shellcheck.net/
Fix each issue, then get the report again.
The result:
#!/bin/bash
if [ -f "$1" ]; then
if [ -d "$2" ] ; then
cp "$1" / "$2"
echo "$4"
fi
else
echo "$3"
exit 1
fi
I still think you are likely to have an issue at line 4 though, when it tries to copy the root directory into arg 2 without -r. I think what you meant was just
cp "$1" "$2"
Also, you have action for the case that someone passes a valid file as $1 but a non-directory as $2. The program will just exit silently and do nothing.

Related

Shell script with absolute path and control errors

I was doing this little script in which the first argument must be a path to an existing directory and the second any other thing.
Each object in the path indicated in the first argument must be renamed so that the new
name is the original that was added as a prefix to the character string passed as the second argument. Example, for the string "hello", the object OBJECT1 is renamed hello.OBJECT1 and so on
Additionally, if an object with the new name is already present, a message is shown by a standard error output and the operation is not carried out continuing with the next object.
I have the following done:
#! /bin/bash
if [ "$#" != 2 ]; then
exit 1
else
echo "$2"
if [ -d "$1" ]; then
echo "directory"
for i in $(ls "$1")
do
for j in $(ls "$1")
do
echo "$i"
if [ "$j" = "$2"."$i" ]; then
exit 1
else
mv -v "$i" "$2"."$i"
echo "$2"."$i"
fi
done
done
else
echo "no"
fi
fi
I am having problems if I run the script from another file other than the one I want to do it, for example if I am in /home/pp and I want the changes to be made in /home/pp/rr, since that is the only way It does in the current.
I tried to change the ls to catch the whole route with
ls -R | sed "s;^;pwd;" but the route catches me badly.
Using find you can't because it puts me in front of the path and doesn't leave the file
Then another question, to verify that that object that is going to create new is not inside, when doing it with two for I get bash errors for all files and not just for coincidences
I'm starting with this scripting, so it has to be a very simple solution thing
An obvious answer to your question would be to put a cd "$2 in the script to make it work. However, there are some opportunities in this script for improvement.
#! /bin/bash
if [ "$#" != 2 ]; then
You might put an error message here, for example, echo "Usage: $0 dir prefix" or even a more elaborate help text.
exit 1
else
echo $2
Please quote, as in echo "$2".
if [ -d $1 ]; then
Here, the quotes are important. Suppose that your directory name has a space in it; then this if would fail with bash: [: a: binary operator expected. So, put quotes around the $1: if [ -d "$1" ]; then
echo "directory"
This is where you could insert the cd "$1".
for i in $(ls $1)
do
It is almost always a bad idea to parse the output of ls. Once again, this for-loop will fail if a file name has a space in it. A possible improvement would be for i in "$1"/* ; do.
for j in $(ls $1)
do
echo $i
if [ $j = $2.$i ]; then
exit 1
else
The logic of this section seems to be: if a file with the prefix exists, then exit instead of overwriting. It is always a good idea to tell why the script fails; an echo before the exit 1 will be helpful.
The question is why you use the second loop? a simple if [ -f "$2.$i ] ; then would do the same, but without the second loop. And it will therefore be faster.
mv -v $i $2.$i
echo $2.$i
Once again: use quotes!
fi
done
done
else
echo "no"
fi
fi
So, with all the remarks, you should be able to improve your script. As tripleee said in his comment, running shellcheck would have provided you with most of the comment above. But he also mentioned basename, which would be useful here.
With all that, this is how I would do it. Some changes you will probably only appreciate in a few months time when you need some changes to the script and try to remember what the logic was that you had in the past.
#!/bin/bash
if [ "$#" != 2 ]; then
echo "Usage: $0 directory prefix" >&2
echo "Put a prefix to all the files in a directory." >&2
exit 1
else
directory="$1"
prefix="$2"
if [ -d "$directory" ]; then
for f in "$directory"/* ; do
base=$(basename "$f")
if [ -f "Sdirectory/$prefix.$base" ] ; then
echo "This would overwrite $prefix.$base; exiting" >&2
exit 1
else
mv -v "$directory/$base" "$directory/$prefix.$base"
fi
done
else
echo "$directory is not a directory" >&2
fi
fi

bash script - ignoring whitespaces in script parameters

I'm quite new to bash scripting and I've ran out of ideas in my homework script.
The script takes 4 arguments - pathToDirectory, [-c/-m/-r] == copy/move/remove, ext1 and ext2 (example of running a script: script.sh /home/user/somefolder -c a.txt b.sh ).
The script should find all files in /home/user/someFolder (and its all subfolders) that contain 'a.txt' in their names and (in -c and -m case) rename that 'a.txt' part to 'b.sh' and depending on -c/-m argument either create a new file or just rename an existing file (in -r case it just removes the file) and then write in stdout something like 'old name => new name'.
example output of a script mentioned above:
/home/user/someFolder/bbb.txt => /home/user/someFolder/bba.txt
Well, that was not a problem to implement, everything worked until I posted my code to our upload system (evaluates our script).
The very first Upload System's try to run my script looked like "script.sh /something/graph 1 -c .jpg .jpeg".
The problem now is, that the whole '/something/graph 1' is a path and that whitespace before '1' ruins it all.
expected output: ./projekty/graph 1.jpg => ./projekty/graph 1.jpeg
my script output: ./projekty/graph => ./projekty/graph.jpeg
1.jpg => 1.jpeg
What I have so far:
if [ "$2" = "-r" ]; then
for file in $(find $1 -name "*$3"); do
echo $file
rm -f $file
done
elif [ "$2" = "-c" ]; then
for file in $(find "$1" -name "*$3") ; do
cp "$file" "${file//$3/$4}"
echo $file "=>" ${file%$3}$4
done
elif [ "$2" = "-m" ]; then
for file in $(find $1 -name "*$3"); do
mv "$file" "${file//$3/$4}"
echo $file "=>" ${file%$3}$4
done
else
echo Unknown parameter >&2
fi
My tried&notworking&probablystupid idea: as the -r/-c/-m parameter should be at $2, I was able to detect that $2 is something else (assumpting something that still belongs to the path) and append that $2 thing to $1, so then I had a variable DIR which was the whole path. Using shift I moved all parameters to the left (because of the whitespace, the -r/-m/-c parameter was not on $2 but on $3, so I made it $2 again) and then the code looked like: (just the -c part)
DIR=$1
if [ "$2" != "-r" ] && [ "$2" != "-c" ] && [ "$2" != "-m" ]; then
DIR+=" $2"
shift
fi
if [ "$2" = "-c" ]; then
for file in $(find "$DIR" -name "*$3") ; do
cp "$file" "${file//$3/$4}"
echo $file "=>" ${file%$3}$4
done
fi
when i echoed "$DIR", it showed the whole path (correctly), but it still didn't work..
Is there any other/better/any way how to fix this please ? :/
Thanks in advance !
As the target string needs to be replaced only at the very end of a filename, "${file//$3/$4}" is a bad idea.
Example: ./projekty/graph.jpg.jpg.jpg.graph.jpg
Passing a string prone to unquoted expansion to a loop is a no better idea either.
The fact is that find works as expected and its output looks like:
./projekty/graph 1.jpg
But inside a loop it is expanded incorrectly:
./projekty/graph
1.jpg
To avoid this, you can save the output of find to a variable and then tokenize it until no text is left:
list="$(find $1 -name "*$3")"
while [ -n "$list" ]; do
file="${list%%$'\n'*}"
list="${list#$file}"
list="${list#$'\n'}"
# your commands here
# ...
done

BASH script accepting parameters

I have to write a script that accepts 1+ source files and destination directory as arguments. I've attempted to write an error message for filenames that contain spaces, but its getting an error when I enter more than 1 argument with a space in between as well. Any help would be appreciated.. This is what I wrote so far:
if [ "$#" -eq "$(echo "$#" | wc -w)" ]
then
echo "Invalid arguments. Filenames may not contain spaces."
echo "usage: bkup file1 [file2...] bkup_directory"
exit 13
fi
You MAY want to try:
if [ $filename == "*" "*" ]; then
echo your error message here
fi
for the testing of spaces in filenames.
As for actually getting the args
$1 is the variable for the first arg and $2 for the second and so on so something like this might work:
if [ $2 == "*" ]; then
echo NO NO NO NOT TODAY!!!
fi
this would check to see if the second argument says anything at all and so if it did we can assume that it is part of the file name (THIS WOULD ONLY WORK IF THE FILENAME IS THE LAST ARGUMENT) OR:
if [ $2 == "*" ]; then
fil=$1 + \
filename=&fil + $2
fi
this would automatically change their filename into an acceptable format for the system an you would not need an error message.
but i am also new to bash so this could not be what you are looking for or I could have the right idea and all this could be complete whooey..... But if I helped then I'm glad I could.

Unexpected end of file bash script

This is just a simple problem but I don't understand why I got an error here. This is just a for loop inside an if statement.
This is my code:
#!/bin/bash
if (!( -f $argv[1])) then
echo "Argv must be text file";
else if ($#argv != 1) then
echo "Max argument is 1";
else if (-f $argv[1]) then
for i in `cut -d ',' -f2 $argv[1]`
do
ping -c 3 $i;
echo "finish pinging host $i"
done
fi
Error is in line 16, which is the line after fi, that is a blank line .....
Can someone please explain why i have this error ????
many, many errors.
If I try to stay close to your example code:
#!/bin/sh
if [ ! -f "${1}" ]
then
echo "Argv must be text file";
else if [ "${#}" -ne 1 ]
then
echo "Max argument is 1";
else if [ -f "${1}" ]
then
for i in $(cat "${1}" | cut -d',' -f2 )
do
ping -c 3 "${i}";
echo "finish pinging host ${i}"
done
fi
fi
fi
another way, exiting each time the condition is not met :
#!/bin/sh
[ "${#}" -ne 1 ] && { echo "There should be 1 (and only 1) argument" ; exit 1 ; }
[ ! -f "${1}" ] && { echo "Argv must be a file." ; exit 1 ; }
[ -f "${1}" ] && {
for i in $(cat "${1}" | cut -d',' -f2 )
do
ping -c 3 "${i}";
echo "finish pinging host ${i}"
done
}
#!/usr/local/bin/bash -x
if [ ! -f "${1}" ]
then
echo "Argument must be a text file."
else
while-loop-script "${1}"
fi
I have broken this up, because I personally consider it extremely bad form to nest one function inside another; or truthfully to even have more than one function in the same file. I don't care about file size, either; I've got several scripts which are 300-500 bytes long. I'm learning FORTH; fractalism in that sense is a virtue.
# while-loop-script
while read line
do
IFS="#"
ping -c 3 "${line}"
IFS=" "
done < "${1}"
Don't use cat in order to feed individual file lines to a script; it will always fail, and bash will try and execute the output as a literal command. I thought that sed printing would work, and it often does, but for some reason it very often substitutes spaces for newlines, which is extremely annoying as well.
The only absolutely bulletproof method of feeding a line to a script that I know of, which will preserve all space and formatting, is to use while-read loops, rather than substituted for cat or for sed loops, as mentioned.
Something else which you will need to do, in order to be sure about preserving whitespace, is to set the internal field seperator (IFS) to something that you know your file will not contain, and then resetting it back to whitespace at the end of the loop.
For every opening if, you must have a corresponding closing fi. This is also true for else if. Better use elif instead
if test ! -f "$1"; then
echo "Argv must be text file";
elif test $# != 1; then
echo "Max argument is 1";
elif test -f "$1"; then
for i in `cut -d ',' -f2 "$1"`
do
ping -c 3 $i;
echo "finish pinging host $i"
done
fi
There's also no argv variable. If you want to access the command line arguments, you must use $1, $2, ...
Next point is $#argv, this evaluates to $# (number of command line args) and argv. This looks a lot like perl.
Furthermore, testing is done with either test ... or [ ... ], not ( ... )
And finally, you should enclose at least your command line arguments in double quotes "$1". If you don't and there is no command line argument, you have for example
test ! -f
instead of
test ! -f ""
This lets the test fail and go on to the second if, instead of echoing the proper message.

For loop to find out if directory exists in unix

I want to use a script that checks whether a list of directories exists or not and at the same time it should print some custom message that I am sending.
For example:
I have a script that validates if directory exists or not:
**check.sh**
for i in $*
if [ -d "$i" ]; then
echo Found <msg-i> directory.
else
echo <msg-i> directory not found.
Now I want to call this script like this:
./check.sh $DIR1 msg1 $Dir2 msg2 $Dir3 msg3
So if DIR1 doesn't exist then I want to display message as "msg1 directory not found", similarly for DIR2 I want to show "msg2 directory not found". Here msg1 and msg2 are something I want to pass as string. How to achieve this? I am using bash shell.
Try this:
while [ -n "$1" ]
do
dir="$1"
msg="$2"
if [ -d "$dir" ]; then
echo "$msg dir FOUND"
else
echo "$msg dir NOT FOUND"
fi
shift 2
done
shift <n> command simply shifts left positional parameters passed to the script of n positions.
For example if you call a script with:
./myscript 1 2 3 4
$1 is "1" and $2 is "2"
but if you shift 2 then $1 is "3" and $2 is "4".
In this way the loop consumes 2 parameters per cycle until $1 parameter is an empty string ( -n "$1").
while condition can be written more elegantly as:
while (( $# ))
obtaining the same result.
You can also check for the second parameter (while [ -n "$2" ]) but this changes the behavior when user provides an odd number of parameters:
in the first case last directory will be checked but you'll have a strange message because $msg il empty
il the second case you'll not have strange messages, but last directory will silently not be checked
Better test parameters at the beginning:
if (( $# % 2 ))
then
echo "Provide an even number of parameters"
exit 1
fi
Chepner Says:
The while condition can simply be (( $# )) (test if the number of positional parameters is non-zero).
Chaitanya Says:
Hi Chepner, thanks for providing alternate solution, can you please tell me how the while condition should actually look like in order to use $# , I tried different ways but it is not working for me.
Here's a quick sample:
while (( $# ))
do
dir=$1
msg=$2
shift 2
[...]
done
The while (( $# )) will be true as long as there are any command line arguments. Doing the shift twice removes arguments from the list. When no more arguments, the while loop ends.
#Zac has the correct answer.
One tip for the message: use a printf format string:
./check.sh dir1 "can't locate %s directory"
and in the script:
if [[ ! -d "$dir" ]]; then
printf "$msg" "$dir"

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