Top: how to cancel current command

top

While browsing processes on a shared server in top I accidentally hit the r key which prompted me with renice. I had no clue what this was going to do with my input and found no way to go back.

I tried ^C, ^D, <ESC> among other things and ended up just typing some garbage like asdf; which got me out. Is there a sane way to cancel a command that you type interactively in top?

Best Answer

When prompted for the PID to renice, entering any value that isn't a positive integer will exit the renice mode with an error message. Once you enter a PID, however, you are stuck entering a priority; any invalid entry will cause the get_int function to return -1, which will set the priority to -1. The only way to avoid entering a priority is to kill top. Ctrl-C should work. Ctrl-D or enter will cause the niceness to be set to -1.

Source: Procps source code

Related Solutions

Linux – How to interpret this top command

I'm copying this from a man page I wrote for plog, since I was trying to make it clear there:

It is important to understand the difference between virtual address space and physical memory in interpreting some of the above statistics. As the name implies, virtual address space is not real; it’s basically a map of all the memory currently allocated to a process. The limit on the size of this map is the same for each processes (generally, 2-4 GB), and it is not accumulated (ie, you may have dozens or hundreds of processes, each with its own 2-4 GB virtual address space, on a system that only actually has 512 MB of physical memory).

Data cannot actually be stored or retrieved from virtual address space; real data requires real, physical memory. It is the kernel’s job to manage one in relation to another. Virtual space stats (VirtualSz, Data+Stack, and Priv&Write) are useful for considering the structure of a process and the relationship to physical memory use, but with regard to amount of RAM actually used, the physical memory stats (ResidentSz, Share, and Proportion) are what counts.

Top doesn't quite have all those metrics, but the VIRT score is virtual address space, RES refers to physical memory as does SHR. If you are concerned about relative memory usage (ie, one process compared to another), the RES score is more relevant.

Certain parts of VIRT are relevant relative to other processes; visors such as openVZ limit containers based on the total amount of private writable address space, not RSS. Top doesn't report this, but pmap and plog do (see the plog manpage for "Priv&Write"; this was actually part of my motive when writing it).

Lum – Top Command – How to reduce the displayed Columns

NOTE: Assuming you have this version of top (procps). You can check with this command:

$ top --version
    top: procps version 3.2.8
usage:  top -hv | -bcisSH -d delay -n iterations [-u user | -U user] -p pid [,pid ...]

procps is often the version of top included with Fedora/CentOS/RHEL and other variants.

Changing columns

If you look in the man page for top you'll see a section titled: "2b. SELECTING and ORDERING Columns". There are keyboard shortcuts for toggling visibility for the different fields/columns.

For example:

  f,o     . Fields/Columns: 'f' add or remove; 'o' change display order
  F or O  . Select sort field
  <,>     . Move sort field: '<' next col left; '>' next col right

You can use the key f while in top to get to a secondary screen where you can specify which columns should be toggled visible or not:

For example:

Current Fields:  ANOPQRSTUVbcdefgjlmyzWHIKX  for window 3:Mem
Toggle fields via field letter, type any other key to return 

* A: PID        = Process Id                                      * W: S          = Process Status
* N: %MEM       = Memory usage (RES)                              * H: PR         = Priority
* O: VIRT       = Virtual Image (kb)                              * I: NI         = Nice value
* P: SWAP       = Swapped size (kb)                               * K: %CPU       = CPU usage
* Q: RES        = Resident size (kb)                              * X: COMMAND    = Command name/line
* R: CODE       = Code size (kb)
...

There are more, these are just a sample. When you're done toggling the columns the way you want, use the Esc to get out of the selection screen.

Saving configuration

You can use the Shift+W to save your changes so they're the defaults:

  W         Write configuration file

The file is stored here, $HOME/.toprc, and looks like this:

$ more .toprc 
RCfile for "top with windows"       # shameless braggin'
Id:a, Mode_altscr=0, Mode_irixps=1, Delay_time=1.000, Curwin=2
Def fieldscur=AEHIoqTWKNMBcdfgjpLrsuvyzX
    winflags=129016, sortindx=19, maxtasks=0
    summclr=2, msgsclr=5, headclr=7, taskclr=7
Job fieldscur=ABcefgjlrstuvyzMKNHIWOPQDX
    winflags=63416, sortindx=13, maxtasks=0
    summclr=6, msgsclr=6, headclr=7, taskclr=6
Mem fieldscur=ANOPQRSTUVbcdefgjlmyzWHIKX
    winflags=65464, sortindx=13, maxtasks=0
    summclr=5, msgsclr=5, headclr=4, taskclr=5
Usr fieldscur=ABDECGfhijlopqrstuvyzMKNWX
    winflags=65464, sortindx=12, maxtasks=0
    summclr=3, msgsclr=3, headclr=2, taskclr=7

See section 5 of the man page for more details, "5. FILES".