I'm trying to use an if [grep] using the exit value to trigger it
to test, from the command line
$ ls ~/dir | grep txt
$ echo $?
0
However when i use it in an if statement in a script, i.e.
if [ ls /some/dir | grep -q pattern ]; then
echo y
fi
It says
line 1: [ missing `]' (the line the if statement was written on)
Why is this happening and is there a way to fix it?
That is because [ is and conditional expression, check the details.
You should use () instead:
if (ls /some/dir | grep -q pattern); then
echo y
fi
Related
Prevent grep returning an error when input doesn't match. I would like it to keep running and not exit with exit code: 1
set -euo pipefail
numbr_match=$(find logs/log_proj | grep "$name" | wc -l);
How could I solve this?
In this individual case, you should probably use
find logs/log_proj -name "*$name*" | wc -l
More generally, you can run grep in a subshell and trap the error.
find logs/log_proj | ( grep "$name" || true) | wc -l
... though of course grep | wc -l is separately an antipattern;
find logs/log_proj | grep -c "$name" || true
I don't know why you are using -e and pipefail when you don't want to have this behaviour. If your goal is just to treat exit code 2 (by grep) as error, but exit code 1 as no-error, you could write a wrapper script around grep, which you
call instead of grep:
#!/bin/bash
# This script behaves exactly like grep, only
# that it returns exit code 0 if there are no
# matching lines
grep "$#"
rc=$?
exit $((rc == 1 ? 0 : rc))
I am trying to execute the command git diff | grep pkg/client/clientset | wc -l and check if the output is more than 0 or not. I have the following script
if [ "$(git diff | grep pkg/client/clientset | wc -l "$i")" -gt "0" ]; then
echo "Hello"
fi
I am getting the following error while executing the script. The error I am getting is
line 29: [: : integer expression expected
Any idea of what can be going wrong?
Comparing the number of output lines to zero is almost always an antipattern. diff and grep both already tell you whether there was a difference (exit code 1) or a match (exit code 0) precisely so you can say
if diff old new; then
echo "There were differences"
fi
if git diff --exit-code; then
echo "There were differences"
fi
if git diff --exit-code pkg/client/clientset; then
echo "There were differences in this specific file"
fi
if git diff | grep -q pkg/client/clientset; then
echo "Hello"
fi
Notice that git diff requires an explicit option to enable this behavior.
-- EDIT --
There were some incorrect statements in the answer, pointed-out by commentators Gordon Davisson and iBug. They have been corrected in this version of the answer. The final conclusion (remove the "$i") remains the same though.
wc -l "$i" will count the lines in the file $i. If you never used i as a variable, then i will be empty and the command will be wc -l "". The output of that will be empty on STDOUT en contain wc: invalid zero-length file name on STDERR. If the variable i is used, wc will most likely complain about a non-existing file. The point is, that wc will not read STDIN.
I also made some incorrect statements about the quoting. As pointed out, between the ( and ), it is a different quoting context. This can be shown as follows:
$ a="$(/usr/bin/echo "hop")"
$ echo $a
hop
$ b=hop
$ a="$(/usr/bin/echo "$b")"
$ echo $a
hop
Just removing "$i" from the wc-l will solve your issue.
if [ "$(git diff | grep pkg/client/clientset | wc -l)" -gt "0" ]; then
echo "Hello"
fi
Only a note, that is to long for a comment:
if [ "$(git diff | grep pkg/client/clientset | wc -l "$i")" -gt "0" ]; then
I think you will test the existence of string pkg/client/clientset to enter the then part. In this case you can use:
if git diff | grep -q pkg/client/clientset; then
grep will only returns a status because option -q. The status is true after the first occurrence of the string. At this point grep stops. And this status is used by if.
Trying to run a command as a variable but I am getting strange results
Expected result "1" :
grep -i nosuid /etc/fstab | grep -iq nfs
echo $?
1
Unexpected result as a variable command:
cmd="grep -i nosuid /etc/fstab | grep -iq nfs"
$cmd
echo $?
0
It seems it returns 0 as the command was correct not actual outcome. How to do this better ?
You can only execute exactly one command stored in a variable. The pipe is passed as an argument to the first grep.
Example
$ printArgs() { printf %s\\n "$#"; }
# Two commands. The 1st command has parameters "a" and "b".
# The 2nd command prints stdin from the first command.
$ printArgs a b | cat
a
b
$ cmd='printArgs a b | cat'
# Only one command with parameters "a", "b", "|", and "cat".
$ $cmd
a
b
|
cat
How to do this better?
Don't execute the command using variables.
Use a function.
$ cmd() { grep -i nosuid /etc/fstab | grep -iq nfs; }
$ cmd
$ echo $?
1
Solution to the actual problem
I see three options to your actual problem:
Use a DEBUG trap and the BASH_COMMAND variable inside the trap.
Enable bash's history feature for your script and use the hist command.
Use a function which takes a command string and executes it using eval.
Regarding your comment on the last approach: You only need one function. Something like
execAndLog() {
description="$1"
shift
if eval "$*"; then
info="PASSED: $description: $*"
passed+=("${FUNCNAME[1]}")
else
info="FAILED: $description: $*"
failed+=("${FUNCNAME[1]}")
done
}
You can use this function as follows
execAndLog 'Scanned system' 'grep -i nfs /etc/fstab | grep -iq noexec'
The first argument is the description for the log, the remaining arguments are the command to be executed.
using bash -x or set -x will allow you to see what bash executes:
> cmd="grep -i nosuid /etc/fstab | grep -iq nfs"
> set -x
> $cmd
+ grep -i nosuid /etc/fstab '|' grep -iq nfs
as you can see your pipe | is passed as an argument to the first grep command.
for d in */ ; do
cd $d
NUM = $(echo ${PWD##*/} | grep -q "*abc*");
if [[ "$NUM" -ne "0" ]]; then
pwd
fi
cd ..
done
Here I'm trying to match a folder name to some substring 'abc' in the name of the folder and check if the output of the grep is not 0. But it gives me an error which reads that NUM: command not found
An error was addressed in comments.
NUM = $(echo ${PWD##*/} | grep -q "*abc*"); should be NUM=$(echo ${PWD##*/} | grep -q "*abc*");.
To clarify, the core problem would be to be able to match current directory name to a pattern.
You can probably simply the code to just
if grep -q "*abc*" <<< "${PWD##*/}" 2>/dev/null; then
echo "$PWD"
# Your rest of the code goes here
fi
You can use the exit code of the grep directly in a if-conditional without using a temporary variable here ($NUM here). The condition will pass if grep was able to find a match. The here-string <<<, will pass the input to grep similar to echo with a pipeline. The part 2>/dev/null is to just suppress any errors (stderr - file descriptor 2) if grep throws!
As an additional requirement asked by OP, to negate the conditional check just do
if ! grep -q "*abc*" <<< "${PWD##*/}" 2>/dev/null; then
I have used the find command for this, but it doesnt return any message when a file is not found.
And I want the search to be recursive and return a message "not found" when a file is not found.
Here's the code I have done so far. Here "input.txt" contains the list of files to be searched.
set `cat input.txt`
echo $#
for i in $#
do
find $HOME -name $i
done
Try this:
listfile=input.txt
exec 3>&1
find | \
grep -f <( sed 's|.*|/&$|' "$listfile" ) | \
tee /dev/fd/3 | \
sed 's|.*/\([^/]*\)$|\1|' | \
grep -v -f - "$listfile" | \
sed 's/$/ Not found/'
exec 3>&-
open file descriptor 3
find the files
see if they're on the list (use sed to
send a copy of the found ones to file descriptor 3
strip off the directory name
get a list of the ones that don't appear
add the "Not found" message
close file descriptor 3
Output looks like:
/path/to/file1
/path/somewhere/file2
foo Not found
bar Not found
No loops necessary.
Whats wrong with using a script. I hope this will do.
#!/bin/bash -f
for i in $#
do
var=`find $HOME -name $i`
if [ -z "$var"]
then
var="File not found"
fi
echo $var
done
You can use the shell builtin 'test' to test the existence of a file. There is also an alternative syntax using square brackets:
if [ -f $a ]; then # Don't forget the semicolon.
echo $a
else
echo 'Not Found'
fi
Here is one way - create a list of all the files to grep against. If your implementation supports
grep -q otherwise use grep [pattern] 2&>1 >/dev/null....
find $HOME -type f |
while read fname
do
echo "$(basename $fname) $fname"
done > /tmp/chk.lis
while read fname
do
grep -q "^$fname" /tmp/chk.lis
[ $? -eq 0 ] && echo "$fname found" || echo "$fname not found"
done < /tmp/chk.lis
All of this is needed because POSIX find does not return an error when a file is not found
perl -nlE'say-f$_?$_:"not found: $_"' file