You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
30 lines
1.1 KiB
30 lines
1.1 KiB
1 year ago
|
#!/bin/sh
|
||
|
|
echo "This spell will teach you the basics of the eval and exec functions in POSIX-compliant Bash"
|
||
|
|
echo "To study the code of the examples, please use the command: cat 11_eval.sh"
|
||
|
|
|
||
|
|
# eval function
|
||
|
|
# The eval function takes a string as an argument and treats it as if it were a command.
|
||
|
|
# It allows the user to dynamically generate and execute commands.
|
||
|
|
|
||
|
|
# Example 1: Using variables in a command
|
||
|
|
ingredient="Dragon's blood"
|
||
|
|
eval "echo Gathering ingredients for the potion: $ingredient"
|
||
|
|
|
||
|
|
# Example 2: Using command substitution
|
||
|
|
eval "echo Today is $(date)"
|
||
|
|
|
||
|
|
# Example 3: Using multiple commands
|
||
|
|
eval "echo Starting spell; sleep 2; echo Spell complete"
|
||
|
|
|
||
|
|
# exec function
|
||
|
|
# The exec function also takes a command as its argument, but it replaces the current shell process with the new command.
|
||
|
|
# This means that the new command will not run in a subshell and any changes made by the new command will affect the current shell.
|
||
|
|
|
||
|
|
# Example 1: Using exec to run a new shell
|
||
|
|
exec /bin/sh
|
||
|
|
|
||
|
|
# Example 2: Using exec to run a command
|
||
|
|
exec echo "This command is being run by exec"
|
||
|
|
|
||
|
|
echo "Spell cast successfully"
|