# The set builtin command FIXME incomplete - text, examples, maybe extended description ## Synopsis set [--abefhkmnptuvxBCHP] <-o OPTIONNAME> [-][--] ## Description `set` is primarily made to - set the positional parameters (see [handling positional parameters](/scripting/posparams)) to `` - set shell attributes with short options (see below) - set shell attributes with long option names (see below) Without any options, `set` displays all shell- and environment-variables (only is POSIX-mode) in a re-usable format `NAME=VALUE`. ### Attributes All attributes below can be switched on using `-X` and switched off using `+X`. This is done because of the historical meaning of the `-` to set flags (true for most commands on UNIX(r)). | Flag | Optionname | Description | |------|----------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | `-a` | `allexport` | Automatically mark new and altered variables to be exported to subsequent environments. | | `-b` | `notify` | Don't wait for the next prompt to print when showing the reports for a terminated background job (only with job control) | | `-e` | `errexit` | When set, the shell exits when a simple command in a command list exits non-zero (`FALSE`). This is not done in situations, where the exit code is already checked (`if`, `while`, `until`, `||`, `&&`) | | `-f` | `noglob` | Disable [pathname expansion](/syntax/expansion/globs) (globbing) | | `-h` | `hashall` | Remembers the location of commands when they're called (hashing). Enabled by default. | | `-k` | `keyword` | Allows to place environment-assignments everywhere in the commandline, not only infront of the called command. | | `-m` | `monitor` | **Monitor mode**. With job control, a short descriptive line is printed when a backgroud job ends. Default is "on" for interactive shells (with job control). | | `-n` | `noexec` | Read and parse but **do not execute commands** - useful for checking scripts for syntax errors. Ignored by interactive shells. | | `-o` | | Set/unset attributes with long option names, e.g. `set -o noglob`. The long option names are in the second column of this table. If no option name is given, all options are printed with their current status. | | `-p` | `privileged` | Turn on privileged mode. | | `-t` | `onecmd` | Exit after reading and executing **one** command. | | `-u` | `nounset` | Treat unset variables as an error when performing parameter expansion. Non-interactive shells exit on this error. | | `-v` | `verbose` | Print shell input lines as they are read - useful for debugging. | | `-x` | `xtrace` | Print commands just before execution - with all expansions and substitutions done, and words marked - useful for debugging. | | `-B` | `braceexpand` | The shell performs [brace expansion](/syntax/expansion/brace) This is on by default. | | `-C` | \`noclobber` | Don't overwrite files on redirection operations. You can override that by specifying the `>|` redirection operator when needed. See [redirection](/syntax/redirection) | | `-E` | `errtrace` | `ERR`-traps are inherited by by shell functions, command substitutions, and commands executed in a subshell environment. | | `-H` | `histexpand` | Enable `!`-style history expansion. Defaults to `on` for interactive shells. | | `-P` | `physical` | Don't follow symlinks when changing directories - use the physical filesystem structure. | | `-T` | `functrace` | `DEBUG`- and `RETURN`-traps are inherited by subsequent environments, like `-E` for `ERR` trap. | | `-` | | "End of options" - all following arguments are assigned to the positional parameters, even when they begin with a dash. `-x` and `-v` options are turned off. Positional parameters are unchanged (unlike using `--`!) when no further arguments are given. | | `--` | | If no arguments follow, the positional parameters are unset. With arguments, the positional parameters are set, even if the strings begin with a `-` (dash) like an option. | | | Long options usable with `-o` without a short equivalent | | | | `emacs` | Use an emacs-style command line editing interface. This is enabled by default when the shell is interactive, unless the shell is started with `--noediting` option. | | | `history` | If set, command historization is done (enabled by default on interactive shells) | | | `ignoreeof` | The effect is as if the shell command `IGNOREEOF=10` had been executed. See [shell variables](/syntax/shellvars). | | | `nolog` | **(currently ignored)** | | | `pipefail` | If set, the exit code from a pipeline is different from the normal ("last command in pipeline") behaviour: `TRUE` when no command failed, `FALSE` when something failed (code of the rightmost command that failed) | | | `posix` | When set, Bash runs in POSIX mode. | | | `vi` | Enables a `vi`-style command line editing interface. | ## Examples Tag a part of a shell script to output debugging information (`-x`): ``` bash #!/bin/bash ... set -x # on ... set +x # off ... ``` ## Portability considerations `set` and its basic behaviour and options are specified by POSIX(r). However, options that influence Bash-specific things are not portable, naturally. ## See also - Internal: [The shopt builtin command](/commands/builtin/shopt)