Linux /Bin/Sh Check If String Contains X

Linux /bin/sh check if string contains X

You can use a case statement:

case "$myvar" in
*string*) echo yes ;;
*       ) echo no ;;
esac

All you have to do is substitute string for whatever you need.

For example:

case "HELLOHELLOHELLO" in
*HELLO* ) echo "Greetings!" ;;
esac

Or, to put it another way:

string="HELLOHELLOHELLO"
word="HELLO"
case "$string" in
*$word*) echo "Match!" ;;
*      ) echo "No match" ;;
esac

Of course, you must be aware that $word should not contain magic glob characters unless you intend glob matching.

How to check if a string contains a substring in Bash

You can use Marcus's answer (* wildcards) outside a case statement, too, if you use double brackets:

string='My long string'
if [[ $string == *"My long"* ]]; then
  echo "It's there!"
fi

Note that spaces in the needle string need to be placed between double quotes, and the * wildcards should be outside. Also note that a simple comparison operator is used (i.e. ==), not the regex operator =~.

How do you tell if a string contains another string in POSIX sh?

Here's yet another solution. This uses POSIX substring parameter expansion, so it works in Bash, Dash, KornShell (ksh), Z shell (zsh), etc.

test "${string#*$word}" != "$string" && echo "$word found in $string"

A functionalized version with some examples:

# contains(string, substring)
#
# Returns 0 if the specified string contains the specified substring,
# otherwise returns 1.
contains() {
    string="$1"
    substring="$2"
    if test "${string#*$substring}" != "$string"
    then
        return 0    # $substring is in $string
    else
        return 1    # $substring is not in $string
    fi
}

contains "abcd" "e" || echo "abcd does not contain e"
contains "abcd" "ab" && echo "abcd contains ab"
contains "abcd" "bc" && echo "abcd contains bc"
contains "abcd" "cd" && echo "abcd contains cd"
contains "abcd" "abcd" && echo "abcd contains abcd"
contains "" "" && echo "empty string contains empty string"
contains "a" "" && echo "a contains empty string"
contains "" "a" || echo "empty string does not contain a"
contains "abcd efgh" "cd ef" && echo "abcd efgh contains cd ef"
contains "abcd efgh" " " && echo "abcd efgh contains a space"

bash - checking if a string contains #

Your code is clearly running with /bin/sh, not bash.

An alternative to [[ $line = *"#"* ]] that works with /bin/sh is case.

Thus, the following will work with /bin/sh, or when invoked with sh yourscript:

#!/bin/sh
while read -r line; do : line="$line"
  case $line in
    *"#"*) echo "Line is commented out: $line";;
    "")    echo "Line is empty" ;;
    *)     key=${line%%=*}
           value=${line#*=}
           eval "$key="'$line'  # unsafe, but works with /bin/sh, which doesn't have better
                                # indirect assignment approaches.
           printf '%s\t\t-\t\t%s\n' "$key" "$value"
           ;;
  esac
done <input_file.ini

---

Alternately, consider putting in a guard to handle the case when your script is invoked with a non-bash shell:

#!/bin/bash
case $BASH_VERSION in
  '')
    echo "ERROR: Run with a non-bash shell" >&2
    if [ "$tried_reexec" ]; then
      echo "ERROR: Already attempted reexec and failed" >&2
      exit 1
    fi
    if [ -s "$0" ]; then
      export tried_reexec=1
      exec bash "$0" "$@"
    fi
  ;;
esac

while read -r line; do
  if [[ $line = *"#"* ]]; then
    echo "Line is Commented out: $line"          
  elif [[ "$line" = "" ]]; then
    echo "Blank line"                       
  else
    key=${line%%=*}; value=${line#*=}
    printf -v "$key" %s "$value"
    printf '%s\t\t-\t\t%s\n' "$key" "$value"
  fi
done <input_file.ini

How to check if a file contains a specific string using Bash

if grep -q SomeString "$File"; then
  Some Actions # SomeString was found
fi

You don't need [[ ]] here. Just run the command directly. Add -q option when you don't need the string displayed when it was found.

The grep command returns 0 or 1 in the exit code depending on
the result of search. 0 if something was found; 1 otherwise.

$ echo hello | grep hi ; echo $?
1
$ echo hello | grep he ; echo $?
hello
0
$ echo hello | grep -q he ; echo $?
0

You can specify commands as an condition of if. If the command returns 0 in its exitcode that means that the condition is true; otherwise false.

$ if /bin/true; then echo that is true; fi
that is true
$ if /bin/false; then echo that is true; fi
$

As you can see you run here the programs directly. No additional [] or [[]].

To check if a variable in Unix contains any of the string mentioned in a file bash shell

Parameter matching can use extended patterns:

#! /bin/bash

check=$(tr '\n' '|' < list_of_terms.txt)
check="@(${check%|})"

for service in Service1 GetFocus WalletLost ; do
    if [[ $service == *$check* ]] ; then
        echo $service matches
    fi
done

In Bash, how can I check if a string begins with some value?

This snippet on the Advanced Bash Scripting Guide says:

# The == comparison operator behaves differently within a double-brackets
# test than within single brackets.

[[ $a == z* ]]   # True if $a starts with a "z" (wildcard matching).
[[ $a == "z*" ]] # True if $a is equal to z* (literal matching).

So you had it nearly correct; you needed double brackets, not single brackets.

---

With regards to your second question, you can write it this way:

HOST=user1
if  [[ $HOST == user1 ]] || [[ $HOST == node* ]] ;
then
    echo yes1
fi

HOST=node001
if [[ $HOST == user1 ]] || [[ $HOST == node* ]] ;
then
    echo yes2
fi

Which will echo

yes1
yes2

Bash's if syntax is hard to get used to (IMO).

Checking if output of a command contains a certain string in a shell script

Test the return value of grep:

./somecommand | grep 'string' &> /dev/null
if [ $? == 0 ]; then
   echo "matched"
fi

which is done idiomatically like so:

if ./somecommand | grep -q 'string'; then
   echo "matched"
fi

and also:

./somecommand | grep -q 'string' && echo 'matched'

---

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