This checks if a file exists:
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File $FILE exists."
else
echo "File $FILE does not exist."
fi
How do I only check if the file does not exist?
The test command (written as [ here) has a "not" logical operator, ! (exclamation mark):
if [ ! -f /tmp/foo.txt ]; then
echo "File not found!"
fi
Bash File Testing
-b filename - Block special file
-c filename - Special character file
-d directoryname - Check for directory Existence
-e filename - Check for file existence, regardless of type (node, directory, socket, etc.)
-f filename - Check for regular file existence not a directory
-G filename - Check if file exists and is owned by effective group ID
-G filename set-group-id - True if file exists and is set-group-id
-k filename - Sticky bit
-L filename - Symbolic link
-O filename - True if file exists and is owned by the effective user id
-r filename - Check if file is a readable
-S filename - Check if file is socket
-s filename - Check if file is nonzero size
-u filename - Check if file set-user-id bit is set
-w filename - Check if file is writable
-x filename - Check if file is executable
How to use:
#!/bin/bash
file=./file
if [ -e "$file" ]; then
echo "File exists"
else
echo "File does not exist"
fi
A test expression can be negated by using the ! operator
#!/bin/bash
file=./file
if [ ! -e "$file" ]; then
echo "File does not exist"
else
echo "File exists"
fi
Negate the expression inside test (for which [ is an alias) using !:
#!/bin/bash
FILE=$1
if [ ! -f "$FILE" ]
then
echo "File $FILE does not exist"
fi
The relevant man page is man test or, equivalently, man [ -- or help test or help [ for the built-in bash command.
Alternatively (less commonly used) you can negate the result of test using:
if ! [ -f "$FILE" ]
then
echo "File $FILE does not exist"
fi
That syntax is described in "man 1 bash" in sections "Pipelines" and "Compound Commands".
[[ -f $FILE ]] || printf '%s does not exist!\n' "$FILE"
Also, it's possible that the file is a broken symbolic link, or a non-regular file, like e.g. a socket, device or fifo. For example, to add a check for broken symlinks:
if [[ ! -f $FILE ]]; then
if [[ -L $FILE ]]; then
printf '%s is a broken symlink!\n' "$FILE"
else
printf '%s does not exist!\n' "$FILE"
fi
fi
It's worth mentioning that if you need to execute a single command you can abbreviate
if [ ! -f "$file" ]; then
echo "$file"
fi
to
test -f "$file" || echo "$file"
or
[ -f "$file" ] || echo "$file"
I prefer to do the following one-liner, in POSIX shell compatible format:
$ [ -f "/$DIR/$FILE" ] || echo "$FILE NOT FOUND"
$ [ -f "/$DIR/$FILE" ] && echo "$FILE FOUND"
For a couple of commands, like I would do in a script:
$ [ -f "/$DIR/$FILE" ] || { echo "$FILE NOT FOUND" ; exit 1 ;}
Once I started doing this, I rarely use the fully typed syntax anymore!!
To test file existence, the parameter can be any one of the following:
-e: Returns true if file exists (regular file, directory, or symlink)
-f: Returns true if file exists and is a regular file
-d: Returns true if file exists and is a directory
-h: Returns true if file exists and is a symlink
All the tests below apply to regular files, directories, and symlinks:
-r: Returns true if file exists and is readable
-w: Returns true if file exists and is writable
-x: Returns true if file exists and is executable
-s: Returns true if file exists and has a size > 0
Example script:
#!/bin/bash
FILE=$1
if [ -f "$FILE" ]; then
echo "File $FILE exists"
else
echo "File $FILE does not exist"
fi
You can do this:
[[ ! -f "$FILE" ]] && echo "File doesn't exist"
or
if [[ ! -f "$FILE" ]]; then
echo "File doesn't exist"
fi
If you want to check for file and folder both, then use -e option instead of -f. -e returns true for regular files, directories, socket, character special files, block special files etc.
You should be careful about running test for an unquoted variable, because it might produce unexpected results:
$ [ -f ]
$ echo $?
0
$ [ -f "" ]
$ echo $?
1
The recommendation is usually to have the tested variable surrounded by double quotation marks:
#!/bin/sh
FILE=$1
if [ ! -f "$FILE" ]
then
echo "File $FILE does not exist."
fi
In
[ -f "$file" ]
the [ command does a stat() (not lstat()) system call on the path stored in $file and returns true if that system call succeeds and the type of the file as returned by stat() is "regular".
So if [ -f "$file" ] returns true, you can tell the file does exist and is a regular file or a symlink eventually resolving to a regular file (or at least it was at the time of the stat()).
However if it returns false (or if [ ! -f "$file" ] or ! [ -f "$file" ] return true), there are many different possibilities:
the file doesn't exist
the file exists but is not a regular file (could be a device, fifo, directory, socket...)
the file exists but you don't have search permission to the parent directory
the file exists but that path to access it is too long
the file is a symlink to a regular file, but you don't have search permission to some of the directories involved in the resolution of the symlink.
... any other reason why the stat() system call may fail.
In short, it should be:
if [ -f "$file" ]; then
printf '"%s" is a path to a regular file or symlink to regular file\n' "$file"
elif [ -e "$file" ]; then
printf '"%s" exists but is not a regular file\n' "$file"
elif [ -L "$file" ]; then
printf '"%s" exists, is a symlink but I cannot tell if it eventually resolves to an actual file, regular or not\n' "$file"
else
printf 'I cannot tell if "%s" exists, let alone whether it is a regular file or not\n' "$file"
fi
To know for sure that the file doesn't exist, we'd need the stat() system call to return with an error code of ENOENT (ENOTDIR tells us one of the path components is not a directory is another case where we can tell the file doesn't exist by that path). Unfortunately the [ command doesn't let us know that. It will return false whether the error code is ENOENT, EACCESS (permission denied), ENAMETOOLONG or anything else.
The [ -e "$file" ] test can also be done with ls -Ld -- "$file" > /dev/null. In that case, ls will tell you why the stat() failed, though the information can't easily be used programmatically:
$ file=/var/spool/cron/crontabs/root
$ if [ ! -e "$file" ]; then echo does not exist; fi
does not exist
$ if ! ls -Ld -- "$file" > /dev/null; then echo stat failed; fi
ls: cannot access '/var/spool/cron/crontabs/root': Permission denied
stat failed
At least ls tells me it's not because the file doesn't exist that it fails. It's because it can't tell whether the file exists or not. The [ command just ignored the problem.
With the zsh shell, you can query the error code with the $ERRNO special variable after the failing [ command, and decode that number using the $errnos special array in the zsh/system module:
zmodload zsh/system
ERRNO=0
if [ ! -f "$file" ]; then
err=$ERRNO
case $errnos[err] in
("") echo exists, not a regular file;;
(ENOENT|ENOTDIR)
if [ -L "$file" ]; then
echo broken link
else
echo does not exist
fi;;
(*) syserror -p "can't tell: " "$err"
esac
fi
(beware the $errnos support was broken with some versions of zsh when built with recent versions of gcc).
There are three distinct ways to do this:
Negate the exit status with bash (no other answer has said this):
if ! [ -e "$file" ]; then
echo "file does not exist"
fi
Or:
! [ -e "$file" ] && echo "file does not exist"
Negate the test inside the test command [ (that is the way most answers before have presented):
if [ ! -e "$file" ]; then
echo "file does not exist"
fi
Or:
[ ! -e "$file" ] && echo "file does not exist"
Act on the result of the test being negative (|| instead of &&):
Only:
[ -e "$file" ] || echo "file does not exist"
This looks silly (IMO), don't use it unless your code has to be portable to the Bourne shell (like the /bin/sh of Solaris 10 or earlier) that lacked the pipeline negation operator (!):
if [ -e "$file" ]; then
:
else
echo "file does not exist"
fi
envfile=.env
if [ ! -f "$envfile" ]
then
echo "$envfile does not exist"
exit 1
fi
To reverse a test, use "!".
That is equivalent to the "not" logical operator in other languages. Try this:
if [ ! -f /tmp/foo.txt ];
then
echo "File not found!"
fi
Or written in a slightly different way:
if [ ! -f /tmp/foo.txt ]
then echo "File not found!"
fi
Or you could use:
if ! [ -f /tmp/foo.txt ]
then echo "File not found!"
fi
Or, presing all together:
if ! [ -f /tmp/foo.txt ]; then echo "File not found!"; fi
Which may be written (using then "and" operator: &&) as:
[ ! -f /tmp/foo.txt ] && echo "File not found!"
Which looks shorter like this:
[ -f /tmp/foo.txt ] || echo "File not found!"
The test thing may count too. It worked for me (based on Bash Shell: Check File Exists or Not):
test -e FILENAME && echo "File exists" || echo "File doesn't exist"
This code also working .
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File '$FILE' Exists"
else
echo "The File '$FILE' Does Not Exist"
fi
The simplest way
FILE=$1
[ ! -e "${FILE}" ] && echo "does not exist" || echo "exists"
This shell script also works for finding a file in a directory:
echo "enter file"
read -r a
if [ -s /home/trainee02/"$a" ]
then
echo "yes. file is there."
else
echo "sorry. file is not there."
fi
sometimes it may be handy to use && and || operators.
Like in (if you have command "test"):
test -b $FILE && echo File not there!
or
test -b $FILE || echo File there!
If you want to use test instead of [], then you can use ! to get the negation:
if ! test "$FILE"; then
echo "does not exist"
fi
You can also group multiple commands in the one liner
[ -f "filename" ] || ( echo test1 && echo test2 && echo test3 )
or
[ -f "filename" ] || { echo test1 && echo test2 && echo test3 ;}
If filename doesn't exit, the output will be
test1
test2
test3
Note: ( ... ) runs in a subshell, { ... ;} runs in the same shell.
I need to make a script that creates soft/symbolic links, but should also detect if links already exist in the '~/linkedfiles' directory, but the problem is that $file also contains sub directories. ($file will look like this: '~/realfiles/files/file23.gz', but I need 'file23.gz' only.) So my question is, how do I remove the sub directories in $file?
Here is some code as an example:
for file in ~/realfiles/files/*.gz
do
echo "Linking file: $file"
ln -s $file ~/linkedfiles
if [ $? -ne 0 ]; then
echo "[FAIL] Linking of $file failed!"
else
echo "[SUCCESS] $file successfully linked."
fi
done
It appears that you want the base name of the path. There are two ways to do that — the classic reliable way is with the basename command, and the modern not-always-reliable way is with a shell parameter expansion.
for file in ~/realfiles/files/*.gz
do
echo "Linking file: $file"
ln -s "$file" "~/linkedfiles/$(basename "$file")"
if [ $? -ne 0 ]
then echo "[FAIL] Linking of $file failed!"
else echo "[SUCCESS] $file successfully linked."
fi
done
Or:
for file in ~/realfiles/files/*.gz
do
echo "Linking file: $file"
ln -s "$file" "~/linkedfiles/${file##*/}"
if [ $? -ne 0 ]
then echo "[FAIL] Linking of $file failed!"
else echo "[SUCCESS] $file successfully linked."
fi
done
In both scripts, the file ~/realfiles/files/file23.gz will be linked to ~/linkedfiles/file23.gz, which is what I think you are after (though there is room to improve the clarity of the question, such as by citing the desired result for the sample file name).
Slight modification of original script would do
for filename in ~/realfiles/files/*.gz
do
echo "Linking file: $file"
[[ -h "~/linkedfiles/${var##*/}" ]] && continue
ln -s "$filename" ~/linkedfiles/
if [ $? -ne 0 ]
then
echo "[FAIL] Linking of $filename failed!"
else
echo "[SUCCESS] $filename successfully linked."
fi
done
Notes
The -h option with if [ checks ] if the file is a symbolic link
${var##*/} gives you the base name. Check [ parameter expansion ].
targetdir="$HOME/linkedfiles"
for filename in $HOME/realfiles/files/*.gz; do
# if filename is a regular file then ...
if [[ -f "${filename}" ]]; then
# if softlink does not exist in target then link it
if [[ ! -h "${targetdir}/${filename##*/}" ]]; then
echo "Linking ${filename}"
ln -s "${filename}" "${targetdir}"
(( $? == 0 )) && echo 'Link created' || echo 'Create link fails'
else
echo "Skipping because ${filename##*/} exists in ${targetdir}"
fi
fi
done
I typed the code the same as The Linux Command Line: A Complete Introduction, page 369
but prompt the error:
line 7 `if[ -e "$FILE" ]; then`
the code is like:
#!/bin/bash
#test file exists
FILE="1"
if[ -e "$FILE" ]; then
if[ -f "$FILE" ]; then
echo :"$FILE is a regular file"
fi
if[ -d "$FILE" ]; then
echo "$FILE is a directory"
fi
else
echo "$FILE does not exit"
exit 1
fi
exit
I want to figure out what introduced the error. How can I modify the code? My system is Ubuntu.
There must be a space between if and [, like this:
#!/bin/bash
#test file exists
FILE="1"
if [ -e "$FILE" ]; then
if [ -f "$FILE" ]; then
echo :"$FILE is a regular file"
fi
...
These (and their combinations) would all be incorrect too:
if [-e "$FILE" ]; then
if [ -e"$FILE" ]; then
if [ -e "$FILE"]; then
These on the other hand are all ok:
if [ -e "$FILE" ];then # no spaces around ;
if [ -e "$FILE" ] ; then # 1 or more spaces are ok
Btw these are equivalent:
if [ -e "$FILE" ]; then
if test -e "$FILE"; then
These are also equivalent:
if [ -e "$FILE" ]; then echo exists; fi
[ -e "$FILE" ] && echo exists
test -e "$FILE" && echo exists
And, the middle part of your script would have been better with an elif like this:
if [ -f "$FILE" ]; then
echo $FILE is a regular file
elif [ -d "$FILE" ]; then
echo $FILE is a directory
fi
(I also dropped the quotes in the echo, as in this example they are unnecessary)
The solution is pretty simple.
Just give space between if and the opening square braces like given below.
if [ -f "$File" ]; then
<code>
fi
I typed the code the same as The Linux Command Line: A Complete Introduction, page 369
but prompt the error:
line 7 `if[ -e "$FILE" ]; then`
the code is like:
#!/bin/bash
#test file exists
FILE="1"
if[ -e "$FILE" ]; then
if[ -f "$FILE" ]; then
echo :"$FILE is a regular file"
fi
if[ -d "$FILE" ]; then
echo "$FILE is a directory"
fi
else
echo "$FILE does not exit"
exit 1
fi
exit
I want to figure out what introduced the error. How can I modify the code? My system is Ubuntu.
There must be a space between if and [, like this:
#!/bin/bash
#test file exists
FILE="1"
if [ -e "$FILE" ]; then
if [ -f "$FILE" ]; then
echo :"$FILE is a regular file"
fi
...
These (and their combinations) would all be incorrect too:
if [-e "$FILE" ]; then
if [ -e"$FILE" ]; then
if [ -e "$FILE"]; then
These on the other hand are all ok:
if [ -e "$FILE" ];then # no spaces around ;
if [ -e "$FILE" ] ; then # 1 or more spaces are ok
Btw these are equivalent:
if [ -e "$FILE" ]; then
if test -e "$FILE"; then
These are also equivalent:
if [ -e "$FILE" ]; then echo exists; fi
[ -e "$FILE" ] && echo exists
test -e "$FILE" && echo exists
And, the middle part of your script would have been better with an elif like this:
if [ -f "$FILE" ]; then
echo $FILE is a regular file
elif [ -d "$FILE" ]; then
echo $FILE is a directory
fi
(I also dropped the quotes in the echo, as in this example they are unnecessary)
The solution is pretty simple.
Just give space between if and the opening square braces like given below.
if [ -f "$File" ]; then
<code>
fi
I'm trying to fit a script for linux onto my WD world edition drive.
The script is written for Bash (debian) but my WD only runs busybox (with ash). Despite this, I have gotten most functionality in there just from using Google. There is only one operator i have not found a counterpart to, the =~ operator
How can i port the functionality of the =~ operator from the old script to ash?
Script:
#! /bin/bash
# posttorrent.sh by Killemov
{
# Log file, file where we tell what events have been processed.
LOG_FILE=/var/log/posttorrent.log
# Username for transmission remote.
TR_USERNAME="username"
# Password for transmission remote.
TR_PASSWORD="password"
# Get current time.
NOW=$(date +%Y-%m-%d\ %H:%M:%S)
# Source directory, should not be changed.
SRC_DIR="${TR_TORRENT_DIR}/${TR_TORRENT_NAME}"
# Directory to store the un-compressed files in..
DEST_DIR="${TR_TORRENT_DIR}/${TR_TORRENT_NAME}/"
# This parameter string could be passed from Transmission in the future.
TR_TORRENT_PARAMETER="EXTRACT SLEEP1h"
echo "text"
if [ -e "$SRC_DIR/keep" ]; then
TR_TORRENT_PARAMETER="$TR_TORRENT_PARAMETER KEEP"
fi
if [ -e "$SRC_DIR/exit" ]; then
TR_TORRENT_PARAMETER="EXIT"
fi
# Actual processing starts here.
if [[ "$TR_TORRENT_PARAMETER" =~ "EXIT" ]]; then
echo $NOW "Exiting $TR_TORRENT_NAME" >> $LOG_FILE
exit 0
fi
echo "text2"
if [[ "$TR_TORRENT_PARAMETER" =~ "EXTRACT" ]]; then
cd $TR_TORRENT_DIR
if [ -d "$SRC_DIR" ]; then
IFS=$'\n'
unset RAR_FILES i
for RAR_FILE in $( find "$SRC_DIR" -iname "*.rar" ); do
if [[ $RAR_FILE =~ .*part.*.rar ]]; then
if [[ $RAR_FILE =~ .*part0*1.rar ]]; then
RAR_FILES[i++]=$RAR_FILE
fi
else
RAR_FILES[i++]=$RAR_FILE
fi
done
unset IFS
if [ ${#RAR_FILES} -gt 0 ]; then
for RAR_FILE in "$(eval \$$RAR_FILES[#])"; do
unrar x -inul "$RAR_FILE" "$DEST_DIR"
if [ $? -gt 0 ]; then
echo $NOW "Error unrarring $TR_TORRENT_NAME" >> $LOG_FILE
transmission-remote -n $TR_USERNAME:$TR_PASSWORD -t$TR_TORRENT_ID --verify --start
exit 0
fi
done
if [[ ! "$TR_TORRENT_PARAMETER" =~ "KEEP" ]]; then
SLEEP=$(expr match "$TR_TORRENT_PARAMETER" '.*SLEEP\([0-9a-zA-Z]*\)')
if [ ${#SLEEP} -gt 0 ]; then
sleep $SLEEP
fi
transmission-remote -n $TR_USERNAME:$TR_PASSWORD -t$TR_TORRENT_ID --remove-and-delete
fi
echo $NOW "Unrarred $TR_TORRENT_NAME" >> $LOG_FILE
fi
fi
fi
} &
(i had some trouble with indirect references, i hoped i fixed that correctly)
Well for the $VARIABLE =~ PATERN you should be able to use the:
echo "$VARIABLE" | grep -E PATTERN
But I think you will have a little bit of trouble with the arithmetical expressions i++ as well - if it's implemented, then you still need to use the i=$(($i + 1)) syntax, if it's not implemented, then the i=$(expr $i + 1) syntax.
I presume you're reason for the IFS=$'\n' is to split the find on newlines, but you're probably better off with issuing the find into a temporary file, and then doing a while read line; do ... done <$tmpfile,
Additionally, I'm not certain if all versions of busybox ash support arrays, so you may have a problem there as well.