Suppose I have a file format I want to save database backups to given as such:
echo "~/backups/$(date +'%Y-%m-%d_%H-%M-%S').sql"
Now how can I specify this result as a filename for output in shell?
mysqldump my_db > ....?
By the way: shell interprets the result of a nested echo command as an executable command/file. So It would seem that:
mysqldump my_db > $(echo "something")
does NOT work. Instead, shell looks for a file called something and tries executing it?
There is no need to use nested echo. You can avoid it:
mysqldump my_db > ~/backups/$(date +'%Y-%m-%d_%H-%M-%S').sql
$(echo "something") is not the problem, while ~ is.
It works fine if you use full path:
echo 'hello world' > $(echo "/home/root/backups/$(date +'%Y-%m-%d_%H-%M-%S').sql")
In case you're interested in how to use ~:
eval "echo 'hello world' > $(echo "~/backups/$(date +'%Y-%m-%d_%H-%M-%S').sql")"
I think there are more possibilities to answer this question:
How to name a file with current time? [duplicate]
--
You can create a file in bash by using different utilities
Using touch
root#ubuntu:~/T/e/s/t# touch $(date +"%T") //you can format time as per your need
Using editor
root#ubuntu:~/T/e/s/t# vi $(date +"%T")
Using redirection
root#ubuntu:~/T/e/s/t# echo "Input for file" > $(date +"%T")
Time format
In place of %T you can use your own time format
Refer: http://man7.org/linux/man-pages/man1/time.1.html
Related
I have a bash script and at certain points I am using echo to put some messages in a log file. The problem that I have is related to the DATE variable which will be static throughout the entire execution of the script.
I have this basic script below to illustrate the problem:
#!/bin/bash
DATE=`date +"%Y-%m-%dT%H:%M:%S%:z"`
echo "script started at $DATE"
echo "doing something"
sleep 2
echo "script finished at $DATE"
If I execute this script, the output of the $DATE variable is the same in both lines. Is there some bash magic that could nicely resolve this without having to replace $DATE with the command itself on each line?
Thanks in advance
Newer versions of the bash/printf builtin have support for generating datetime stamps without the need to spawn a subprocess to call date:
$ builtin printf --help
...snip...
Options:
-v var assign the output to shell variable VAR rather than
display it on the standard output
...snip...
In addition to the standard format specifications described in printf(1),
printf interprets:
%b expand backslash escape sequences in the corresponding argument
%q quote the argument in a way that can be reused as shell input
%(fmt)T output the date-time string resulting from using FMT as a format
string for strftime(3)
... snip ...
Instead of spawning a subprocess to call date, eg:
logdt=`date +"%Y-%m-%dT%H:%M:%S:%z"`
The same can be accomplished via printf -v by wrapping the desired format in %(...)T, eg:
printf -v logdt '%(%Y-%m-%dT%H:%M:%S:%z)T'
NOTE: assuming %:z should be :%z
Assuming you'll be tagging a lot of lines with datetime stamps then the savings from eliminating the subproces date calls could be huge.
Running a test of 1000 datetime stamp generations:
$ time for ((i=1;i<=1000;i++)); do { printf -v logdt '%(...)T' | logdate=$(date ...) }; done
Timings for printf -v logdt '%(...)T':
real 0m0.182s # ~130 times faster than $(date ...)
user 0m0.171s
sys 0m0.000s
Timings for logdt=$(date ...):
real 0m24.443s # ~130 times slower than printf -v
user 0m5.533s
sys 0m16.724s
With bash version 4.3+ , you can use the builtin printf to format datetimes. -1 below is a magic value that means "now".
#!/bin/bash
datefmt='%Y-%m-%dT%H:%M:%S%z'
printf "script started at %($datefmt)T\n" -1
echo "doing something"
sleep 2
printf "script finished at %($datefmt)T\n" -1
bash didn't recognize %:z for me.
This can help you:
#!/bin/bash
echo "script started at $(date +'%Y-%m-%dT%H:%M:%S%:z')"
echo "doing something"
sleep 2
echo "script finished at $(date +'%Y-%m-%dT%H:%M:%S%:z')"
You might want to create an alias if calling the full command looks clumsy to you.
This is my script , even after using the export command not able to use variable outside of the block. Below is the code that i have tried. I also tried other option like declare -x var, but that is also not working.
Can someone please please comment on this , am i doing right ?
#!/bin/bash
{
var="123"
export var # exporting the variable so that i can access from anywhere
echo "var is "$var # able to get the value of this variable
} | tee log.txt
echo "var is "$var # not able to get the value of this variable
Because the pipe is causing the code between the braces to execute in a sub-shell you need to find a way to capture that data as opposed to storing it in a variable that is not accessible from the rest of the code. An example would be to store the output of a function in a variable, or to access it via command substitution. If you have script.sh as such:
#!/bin/bash
function get_pizza() {
echo "Pizza"
}
myvar=$(get_pizza)
printf "myvar is '%s'\n" $myvar
echo "Plain echo follows:"
echo $(get_pizza)
and then run bash script.sh you will get output as such:
[user#host]$ bash ./script.sh
myvar is 'Pizza'
Plain echo follows:
Pizza
Then if you still want to write to a file via tee, you can pipe your whole script to tee:
bash ./script.sh | tee foo.log
If you only want parts of the script to goto a file, you'll can also handle that with I/O redirection within the script: echo pizza > foo.log
please bear with me if my terminology or syntax is less than stellar (still learning). I currently have a simple bash script that checks the arguments of the command and outputs files names with matching text. This part of my script works correctly via a grep command and piped to xargs for proper formatting.
When running the script, I run through a simple loop to check if the value is null and then move to running my variable/search if not.
My question is: Is it possible to have this script output via stdout AND also save a new file each time it is run with the user input and date/time? (but not overwrite) EX: report-bob-0729161500.rpt
I saw same other suggestions to use tee with the command, but I was trying to get it to work within the script. Similarly, another suggestion stated to utilize exec > >(tee -i logfile.txt), but I am unsure how to properly format this to include the date/time and $1 input into new files each time the script is executed.
Any help or suggested resources?
Thank you.
SEARCH=`[search_variable]`
if [ -z "$SEARCH" ]
then
echo "$1 not found."
else
echo -e "REPORT LISTING\n\n"
echo "$SEARCH"
fi
EDIT: I did try simply piping the echo statements to the tee command, which does work. However, I am still curious if anyone has other suggestions to accomplish this same task via alternative methods. Thank you.
With echo statements piped to tee:
SEARCH=`[search_variable]`
DATE=`date +"%m%d%y%k%M"`
if [ -z "$SEARCH" ]
then
echo "$1 not found."
else
echo -e "REPORT LISTING\n\n" | tee tps-list-$1-$DATE.rpt
echo "$SEARCH" | tee tps-list-$1-$DATE.rpt
fi
If you want to do it within the script, why then not just write to
both standard output and the file (using append where appropriate?).
Maybe a bit more writing, but it gives complete control.
Leon
my server is using CentOS 5.5 (which is almost Red Hat Linux).
I want to backup a set of pictures into time-stamped files.
This code would work:
z_cmd1=$(tar cvzf /home/user1/public_ftp/misc/pics_20100925_142230.tar.gz /home/user1/public_html/misc/_pics_var/F???????.jpg)
echo "tar output =[${z_cmd1}]"
but of course I want the time stamp to be automatic.
The following code does not work. Somehow, the third line (the one with the tar) fails. 'tar' does something, but it does not create any file at the expected destination folder. Why?
z_fname=$(date +"/home/user1/public_ftp/misc/pics_%Y%m%d_%H%M%S.tar.gz")
echo "File name =[${z_fname}]"
z_cmd1=$(tar cvzf ${z_fname} /home/user1/public_html/misc/_pics_var/F???????.jpg)
echo "tar output =[${z_cmd1}]"
Thank you.
Try this something like this:
mydate=`date +"%m-%d-%Y"`;
input="/home/user1/public_html/misc/_pics_var/F???????.jpg";
output="/home/user1/public_ftp/misc/pics_$mydate.tar.gz";
tar cvzf $output $input && echo "$output created succesfully!";
if [ ! $? == 0 ]; then echo "$output failed"; fi;
We create a date as variable.
We create the input and output variables, using the date variable in the output variable.
Then execute the command and check if it executed without errors.
I'm converting some Windows batch files to Unix scripts using sh. I have problems because some behavior is dependent on the %~dp0 macro available in batch files.
Is there any sh equivalent to this? Any way to obtain the directory where the executing script lives?
The problem (for you) with $0 is that it is set to whatever command line was use to invoke the script, not the location of the script itself. This can make it difficult to get the full path of the directory containing the script which is what you get from %~dp0 in a Windows batch file.
For example, consider the following script, dollar.sh:
#!/bin/bash
echo $0
If you'd run it you'll get the following output:
# ./dollar.sh
./dollar.sh
# /tmp/dollar.sh
/tmp/dollar.sh
So to get the fully qualified directory name of a script I do the following:
cd `dirname $0`
SCRIPTDIR=`pwd`
cd -
This works as follows:
cd to the directory of the script, using either the relative or absolute path from the command line.
Gets the absolute path of this directory and stores it in SCRIPTDIR.
Goes back to the previous working directory using "cd -".
Yes, you can! It's in the arguments. :)
look at
${0}
combining that with
{$var%Pattern}
Remove from $var the shortest part of $Pattern that matches the back end of $var.
what you want is just
${0%/*}
I recommend the Advanced Bash Scripting Guide
(that is also where the above information is from).
Especiall the part on Converting DOS Batch Files to Shell Scripts
might be useful for you. :)
If I have misunderstood you, you may have to combine that with the output of "pwd". Since it only contains the path the script was called with!
Try the following script:
#!/bin/bash
called_path=${0%/*}
stripped=${called_path#[^/]*}
real_path=`pwd`$stripped
echo "called path: $called_path"
echo "stripped: $stripped"
echo "pwd: `pwd`"
echo "real path: $real_path
This needs some work though.
I recommend using Dave Webb's approach unless that is impossible.
In bash under linux you can get the full path to the command with:
readlink /proc/$$/fd/255
and to get the directory:
dir=$(dirname $(readlink /proc/$$/fd/255))
It's ugly, but I have yet to find another way.
I was trying to find the path for a script that was being sourced from another script. And that was my problem, when sourcing the text just gets copied into the calling script, so $0 always returns information about the calling script.
I found a workaround, that only works in bash, $BASH_SOURCE always has the info about the script in which it is referred to. Even if the script is sourced it is correctly resolved to the original (sourced) script.
The correct answer is this one:
How do I determine the location of my script? I want to read some config files from the same place.
It is important to realize that in the general case, this problem has no solution. Any approach you might have heard of, and any approach that will be detailed below, has flaws and will only work in specific cases. First and foremost, try to avoid the problem entirely by not depending on the location of your script!
Before we dive into solutions, let's clear up some misunderstandings. It is important to understand that:
Your script does not actually have a location! Wherever the bytes end up coming from, there is no "one canonical path" for it. Never.
$0 is NOT the answer to your problem. If you think it is, you can either stop reading and write more bugs, or you can accept this and read on.
...
Try this:
${0%/*}
This should work for bash shell:
dir=$(dirname $(readlink -m $BASH_SOURCE))
Test script:
#!/bin/bash
echo $(dirname $(readlink -m $BASH_SOURCE))
Run test:
$ ./somedir/test.sh
/tmp/somedir
$ source ./somedir/test.sh
/tmp/somedir
$ bash ./somedir/test.sh
/tmp/somedir
$ . ./somedir/test.sh
/tmp/somedir
This is a script can get the shell file real path when executed or sourced.
Tested in bash, zsh, ksh, dash.
BTW: you shall clean the verbose code by yourself.
#!/usr/bin/env bash
echo "---------------- GET SELF PATH ----------------"
echo "NOW \$(pwd) >>> $(pwd)"
ORIGINAL_PWD_GETSELFPATHVAR=$(pwd)
echo "NOW \$0 >>> $0"
echo "NOW \$_ >>> $_"
echo "NOW \${0##*/} >>> ${0##*/}"
if test -n "$BASH"; then
echo "RUNNING IN BASH..."
SH_FILE_RUN_PATH_GETSELFPATHVAR=${BASH_SOURCE[0]}
elif test -n "$ZSH_NAME"; then
echo "RUNNING IN ZSH..."
SH_FILE_RUN_PATH_GETSELFPATHVAR=${(%):-%x}
elif test -n "$KSH_VERSION"; then
echo "RUNNING IN KSH..."
SH_FILE_RUN_PATH_GETSELFPATHVAR=${.sh.file}
else
echo "RUNNING IN DASH OR OTHERS ELSE..."
SH_FILE_RUN_PATH_GETSELFPATHVAR=$(lsof -p $$ -Fn0 | tr -d '\0' | grep "${0##*/}" | tail -1 | sed 's/^[^\/]*//g')
fi
echo "EXECUTING FILE PATH: $SH_FILE_RUN_PATH_GETSELFPATHVAR"
cd "$(dirname "$SH_FILE_RUN_PATH_GETSELFPATHVAR")" || return 1
SH_FILE_RUN_BASENAME_GETSELFPATHVAR=$(basename "$SH_FILE_RUN_PATH_GETSELFPATHVAR")
# Iterate down a (possible) chain of symlinks as lsof of macOS doesn't have -f option.
while [ -L "$SH_FILE_RUN_BASENAME_GETSELFPATHVAR" ]; do
SH_FILE_REAL_PATH_GETSELFPATHVAR=$(readlink "$SH_FILE_RUN_BASENAME_GETSELFPATHVAR")
cd "$(dirname "$SH_FILE_REAL_PATH_GETSELFPATHVAR")" || return 1
SH_FILE_RUN_BASENAME_GETSELFPATHVAR=$(basename "$SH_FILE_REAL_PATH_GETSELFPATHVAR")
done
# Compute the canonicalized name by finding the physical path
# for the directory we're in and appending the target file.
SH_SELF_PATH_DIR_RESULT=$(pwd -P)
SH_FILE_REAL_PATH_GETSELFPATHVAR=$SH_SELF_PATH_DIR_RESULT/$SH_FILE_RUN_BASENAME_GETSELFPATHVAR
echo "EXECUTING REAL PATH: $SH_FILE_REAL_PATH_GETSELFPATHVAR"
echo "EXECUTING FILE DIR: $SH_SELF_PATH_DIR_RESULT"
cd "$ORIGINAL_PWD_GETSELFPATHVAR" || return 1
unset ORIGINAL_PWD_GETSELFPATHVAR
unset SH_FILE_RUN_PATH_GETSELFPATHVAR
unset SH_FILE_RUN_BASENAME_GETSELFPATHVAR
unset SH_FILE_REAL_PATH_GETSELFPATHVAR
echo "---------------- GET SELF PATH ----------------"
# USE $SH_SELF_PATH_DIR_RESULT BEBLOW
I have tried $0 before, namely:
dirname $0
and it just returns "." even when the script is being sourced by another script:
. ../somedir/somescript.sh