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Fundamental of a bash builtin command named “unalias”

ABOUT unalias Remove each name from the list of defined aliases. If -a is supplied, all alias definitions are removed. The return value is true unless a supplied name is not a defined alias. [bash] $unalias unalias: usage: unalias [-a] name [name ...] $echo $? 2 $unalias -a $echo $? 0 $unalias pwd bash: unalias:… Continue reading Fundamental of a bash builtin command named “unalias”

Simple example of a bash builtin command named “wait”

ABOUT wait wait waits for the process identified by process ID pid (or the job specified by job ID jobid), and reports its termination status. If an ID is not given, wait waits for all currently active child processes, and the return status is zero. If the ID is a job specification, wait waits for… Continue reading Simple example of a bash builtin command named “wait”

A look into the bash builtin command named “until”

ABOUT until until command in Linux used to execute a set of commands as long as the final command in the ‘until’ Commands has an exit status which is not zero. It is mostly used where the user needs to execute a set of commands until a condition is true. A TYPICAL SHELL EXPOSURE [bash]… Continue reading A look into the bash builtin command named “until”

Sessions of bash builtin command named “times”

ABOUT times Print the accumulated user and system times for the shell and for processes run from the shell [bash] $times 0m0.063s 0m0.024s 0m0.008s 0m0.012s $times pin 0m0.064s 0m0.025s 0m0.008s 0m0.012s $times ping 0m0.065s 0m0.025s 0m0.008s 0m0.012s $times --help times: times Display process times. Prints the accumulated user and system times for the shell and… Continue reading Sessions of bash builtin command named “times”

Fundamentals related to a bash builtin command named “test”

ABOUT test test provides no output, but returns 0 for "true" (test successful) and 1 for "false" (test failed). RELATED COMMAND LINE EXPOSURE [bash] $num=10; if (test $num -gt 5); then echo "yes"; else echo "no"; fi yes $num=1; if (test $num -gt 5); then echo "yes"; else echo "no"; fi no $num=5; if (test… Continue reading Fundamentals related to a bash builtin command named “test”

Fundamentals related to bash builtin command named “shift”

ABOUT shift shift [n] The positional parameters from n+1 ... are renamed to $1 .... Parameters represented by the numbers $# down to $#-n+1 are unset. n must be a non-negative number less than or equal to $#. If n is 0, no parameters are changed. If n is not given, it is assumed to… Continue reading Fundamentals related to bash builtin command named “shift”

Understanding bash fundamentals and also about return command

ABOUT return Causes a function to stop executing and return the value specified by n to its caller. If n is omitted, the return status is that of the last command executed in the function body. TYPICAL COMMAND LINE EXPOSURE [bash] $cat learn function e() { echo hello echo "10" } e value=e #echo $value… Continue reading Understanding bash fundamentals and also about return command

About bash builtin command named “eval”

ABOUT eval eval is a builtin command of the Bash shell. It concatenates its arguments into a single string, joining the arguments with spaces, then executes that string as a bash command. It's similar to running bash -c "string", but eval executes the command in the current shell environment rather than creating a child shell… Continue reading About bash builtin command named “eval”