Add scripts to filter and count files by uppercase letter patterns

- script-01.sh: List files with at least one uppercase letter in the name.
- script-02.sh: List files whose names start with an uppercase letter.
- script-03.sh: List files whose names start with an uppercase letter and have no other uppercase letters.
- script-04.sh: Count files matching the pattern from script-03.sh.

Author: Iswanna

shell-pipelines/ls-grep/script-01.sh

@@ -4,3 +4,5 @@ set -euo pipefail
 
 # TODO: Write a command to output the names of the files in the sample-files directory whose name contains at least one upper case letter.
 # Your output should contain 11 files.
+
+ls ./sample-files | grep '[A-Z]' 

shell-pipelines/ls-grep/script-02.sh

@@ -4,3 +4,5 @@ set -euo pipefail
 
 # TODO: Write a command to output the names of the files in the sample-files directory whose name starts with an upper case letter.
 # Your output should contain 10 files.
+
+ls ./sample-files | grep '^[A-Z]'

shell-pipelines/ls-grep/script-03.sh

@@ -4,3 +4,5 @@ set -euo pipefail
 
 # TODO: Write a command to output the names of the files in the sample-files directory whose name starts with an upper case letter and doesn't contain any other upper case letters.
 # Your output should contain 7 files.
+
+ls ./sample-files | grep '^[A-Z][^A-Z]*$'

shell-pipelines/ls-grep/script-04.sh

@@ -4,3 +4,5 @@ set -euo pipefail
 
 # TODO: Write a command to count the number of files in the sample-files directory whose name starts with an upper case letter and doesn't contain any other upper case letters.
 # Your output should be the number 7.
+
+ls ./sample-files | grep -c '^[A-Z][^A-Z]*$'