So im trying to make an infinity loop, that creates libraries.
but the file variable take input only once.
code:
for (( ; ; ))
do
file=${1?Error: no input}
mkdir "$file"
sleep 1
done
There's nothing in that loop that asks for input. $1 is provided once by the user as they run the script (before the loop even starts). The standard way to request input in a shell script is with the read command. Something like this:
while read -p "Enter a directory to create: " file; do
mkdir "$file"
done
This loop will terminate when it receives an end-of-file, which means the user must press Control-D to exit it. If you want to exit if the user just presses return without entering anything, you could do this:
while read -p "Enter a directory to create: " file; do
if [ -z "$file" ]; then
echo "Error: no input" >&2
break # This exits the while loop
fi
mkdir "$file"
done
Related
I am trying to create a loop to prompt the user to create a file. If the file already exists, it will keep prompting the user until the user enters a file that does not exist. But can't seem to get it to work, anyone can help, please?
file3=/root/simulate/$filename
while true ; do
if [ ! -f "$file3" ]; then
read -p "Please enter a file name to create in simulate folder:" filename
touch /root/simulate/$filename
elif [ -f "$file3" ]; then
read -p "Please enter a different file name as $filename already exist:" filename
touch /root/simulate/$filename
break
else
touch /root/simulate/$filename
fi
done
filename variable is empty.
There are two way to fill in filename variable
filename variable can pass on shell script by export command.
ex) $export filename=newFile
if you execute shell script, shell is forking and execute new shell. new shell taken your mother shell's Environment variables
Push filename variable into shell script.
note: I picked second way and I changed path of $file3.
I fixed codes in block of elif to ask again if something goes wrong.
this is a code.
#!/bin/bash
filename=newFile
file3="./$filename"
while true ; do
if [ ! -f "$file3" ]; then
read -p "Please enter a file name to create in simulate folder:" filename
touch ./$filename
break
elif [ -f "$file3" ]; then
while true ; do
read -p "Please enter a different file name as $filename already exist:" filename
if [ ! -f "$filename" ]; then
touch ./$filename
break 2
fi
done
else
touch ./$filename
fi
done
I'm automating the file creation from a bash script. I generated a file rc_notes.txt which has commit messages from two tags and want to re-write that in a new file as rc_device.txt.
I want the user to write the customer release notes and exit from the BASH STDIN that I prompt in the terminal.
The problem in my script is I'm not able to trap the close of file.
Wondering how to do. I don't want to trap the close signal. I want to enter magic string example: Done or some string that triggers the closure of STDIN, that exit from the script gracefully.
My script:
#/bin/bash
set -e
echo "Creating the release candiate text"
rc_file=rc_updater_notes.txt
echo "=========Reading the released commit message file=========="
cat $rc_file
echo "=========End of the commit message file=========="
echo "Now write the release notes"
#exec < /dev/tty
while read line
do
echo "$line"
done < "${1:-/dev/stdin}" > rc_file.txt
It does create the file but I need to exit manually by entering ctrl+D or ctrl+z. I don't want to do that. Any suggestions?
To break the loop when "Done" is entered
while read line
do
if [[ $line = Done ]]; then
break;
fi
echo "$line"
done < "${1:-/dev/stdin}" > rc_file.txt
or
while read line && [[ $line != Done ]]
do
echo "$line"
done < "${1:-/dev/stdin}" > rc_file.txt
I want a Bash script to generate some output messages. The script is supposed to capture messages, do some filtering, transform, and then output them to the screen.
The filtered results are correct in the output, but the script is not terminated. I must press a return key to finish it. How do I fix it?
Demo script:
#!/bin/bash
exec &> >(
{
while read line; do
[ "$line" = "exit" ] && break
echo "`date +%H:%M:%S.%N` $line"
done
echo "while finish"
} )
for ((i=3;i--;)); do
echo "text $i"
done
echo "exit"
The script does terminate, but the script itself finishes before the background process that writes the output does, so the prompt is displayed first, then the output, leaving your terminal with a blank line that looks like the script is still running. You could type any command instead of hitting return, and that command would execute.
To avoid this, you need to run the while loop in an explicit background job that you can wait on before exiting your script.
mkfifo logpipe
trap 'wait $logger_pid; rm logpipe' EXIT
while read line; do
[ "$line" = "exit" ] && break
echo "$(date +%H:%M:%S.%N) $line"
done < logpipe &
logger_pid=$!
exec &> logpipe
# ==========
for ((i=3;i--;)); do
echo "text $i"
done
echo "exit"
The while loop runs in the background, reading its input from the named pipe logpipe. Once that is running, you can redirect all your output to the pipe and start your "main" script. The exit trap ensures that your script doesn't actually exit until the while loop completes; it also cleans up the named pipe for you.
You might not have noticed yet, but there is no guarantee that the while loop will receive the merged standard output and standard error in the exact order in which things are written to them. For instance,
echo out1
echo err1 >&2
echo out2
echo err2 >&2
may end up being read as
out1
err1
err2
out2
Each stream itself will remain in order, but the two could be arbitrarily merged.
Every time I run this code I get the error File or directory doesn't exist. Why?
read -p "Enter the filename/path of the file you wish to delete : " filename
echo "Do you want to delete this file"
echo "Y/N"
read ans
case "$ans" in
Y) "`readlink -f $filename`" >>~/TAM/store & mv $filename ~/TAM/dustbin
echo "File moved" ;;
N) "File Not deleted" ;;
esac
When I enter the file name/directory exactly and triple check its right I still get this error, but the readlink part works.
Paraphrasing/summarizing/extending my answer for a similar question:
I doubt you really meant to use & instead of && in your script.
"File Not deleted" is not a valid command on any Linux system that I have used. Perhaps you are missing an echo there?
You have to fix your variable quotation. If the filename variable contains whitespace, then $filename is expanded by the shell into more than one arguments. You need to enclose it into double quotes:
mv "$filename" ~/TAM/dustbin
I do not see your script creating the ~/TAM/ directory anywhere...
You are missing an echo and one &&.
Use echo "`command`" to pipe the result string of commands. Alternatively, you may directly use the command without backticks and quotes, (not storing the result in a string), in which case you do not need an echo because the command will pipe its result to the next command.
The single & will run the preceding command in the background (async.). To check for return values and conditionally execute you need && and ||.
Here is a complete solution/example (incl. some more logging):
# modified example not messing the $HOME dir.
# should be save to run in a separate dir
touch testfile #create file for testing
read -p "Enter the filename/path of the file you wish to delete : " filename
echo "Do you want to delete this file: $filename"
echo "Y/N"
read ans
touch movedfiles #create a file to store the moved files
[ -d _trash ] || mkdir _trash #create a dustbin if not already there
case "$ans" in
Y) readlink -f "$filename" >> movedfiles && echo "File name stored" &&
mv "$filename" _trash && echo "File moved" ;;
N) echo "File Not deleted" ;;
esac
cat movedfiles #display all moved files
I have a bash program that will write to an output file. This file may or may not exist, but the script must check permissions and fail early. I can't find an elegant way to make this happen. Here's what I have tried.
set +e
touch $file
set -e
if [ $? -ne 0 ]; then exit;fi
I keep set -e on for this script so it fails if there is ever an error on any line. Is there an easier way to do the above script?
Why complicate things?
file=exists_and_writeable
if [ ! -e "$file" ] ; then
touch "$file"
fi
if [ ! -w "$file" ] ; then
echo cannot write to $file
exit 1
fi
Or, more concisely,
( [ -e "$file" ] || touch "$file" ) && [ ! -w "$file" ] && echo cannot write to $file && exit 1
Rather than check $? on a different line, check the return value immediately like this:
touch file || exit
As long as your umask doesn't restrict the write bit from being set, you can just rely on the return value of touch
You can use -w to check if a file is writable (search for it in the bash man page).
if [[ ! -w $file ]]; then exit; fi
Why must the script fail early? By separating the writable test and the file open() you introduce a race condition. Instead, why not try to open (truncate/append) the file for writing, and deal with the error if it occurs? Something like:
$ echo foo > output.txt
$ if [ $? -ne 0 ]; then die("Couldn't echo foo")
As others mention, the "noclobber" option might be useful if you want to avoid overwriting existing files.
Open the file for writing. In the shell, this is done with an output redirection. You can redirect the shell's standard output by putting the redirection on the exec built-in with no argument.
set -e
exec >shell.out # exit if shell.out can't be opened
echo "This will appear in shell.out"
Make sure you haven't set the noclobber option (which is useful interactively but often unusable in scripts). Use > if you want to truncate the file if it exists, and >> if you want to append instead.
If you only want to test permissions, you can run : >foo.out to create the file (or truncate it if it exists).
If you only want some commands to write to the file, open it on some other descriptor, then redirect as needed.
set -e
exec 3>foo.out
echo "This will appear on the standard output"
echo >&3 "This will appear in foo.out"
echo "This will appear both on standard output and in foo.out" | tee /dev/fd/3
(/dev/fd is not supported everywhere; it's available at least on Linux, *BSD, Solaris and Cygwin.)