Blink Code Removal – Understanding Escape Codes

ansi-termescape-characters

According to Bash tips: Colors and formatting (ANSI/VT100 Control sequences) I attemped to active blink code in my program, But may be blink code has been eliminated. Is it true?

If is not true, Please help me to use blink code.

Best Answer

The blink feature depends upon the terminal (or terminal emulator). Most terminals you will use accept the control sequences documented in ECMA-48, e.g., VT100-compatible. The control sequence may

  • cause blinking on a given terminal, or
  • show as a particular color, or
  • simply ignored by a given terminal

Applications usually use a terminal description (terminfo or termcap). If the terminal description does not tell how to blink, then the application will not know either.

If your computer has infocmp (for terminfo), that will show the capabilities listed in the terminal description. bash only looks for blink — using the termcap name, since it is a termcap application. More generally, terminfo can also describe how to blink using sgr (which is not available in termcap descriptions).

For example, this is a terminfo description of vt100:

> infocmp vt100
#       Reconstructed via infocmp from file: /usr/local/ncurses/share/terminfo/v/vt100
vt100|vt100-am|dec vt100 (w/advanced video),
        am, mc5i, msgr, xenl, xon,
        cols#80, it#8, lines#24, vt#3,
        acsc=``aaffggjjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
        bel=^G, blink=\E[5m$<2>, bold=\E[1m$<2>,
        clear=\E[H\E[J$<50>, cr=^M, csr=\E[%i%p1%d;%p2%dr,
        cub=\E[%p1%dD, cub1=^H, cud=\E[%p1%dB, cud1=^J,
        cuf=\E[%p1%dC, cuf1=\E[C$<2>,
        cup=\E[%i%p1%d;%p2%dH$<5>, cuu=\E[%p1%dA,
        cuu1=\E[A$<2>, ed=\E[J$<50>, el=\E[K$<3>, el1=\E[1K$<3>,
        enacs=\E(B\E)0, home=\E[H, ht=^I, hts=\EH, ind=^J, ka1=\EOq,
        ka3=\EOs, kb2=\EOr, kbs=^H, kc1=\EOp, kc3=\EOn, kcub1=\EOD,
        kcud1=\EOB, kcuf1=\EOC, kcuu1=\EOA, kent=\EOM, kf0=\EOy,
        kf1=\EOP, kf10=\EOx, kf2=\EOQ, kf3=\EOR, kf4=\EOS, kf5=\EOt,
        kf6=\EOu, kf7=\EOv, kf8=\EOl, kf9=\EOw, lf1=pf1, lf2=pf2,
        lf3=pf3, lf4=pf4, mc0=\E[0i, mc4=\E[4i, mc5=\E[5i, rc=\E8,
        rev=\E[7m$<2>, ri=\EM$<5>, rmacs=^O, rmam=\E[?7l,
        rmkx=\E[?1l\E>, rmso=\E[m$<2>, rmul=\E[m$<2>,
        rs2=\E>\E[?3l\E[?4l\E[?5l\E[?7h\E[?8h, sc=\E7,
        sgr=\E[0%?%p1%p6%|%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;m%?%p9%t\016%e\017%;$<2>,
        sgr0=\E[m\017$<2>, smacs=^N, smam=\E[?7h, smkx=\E[?1h\E=,
        smso=\E[7m$<2>, smul=\E[4m$<2>, tbc=\E[3g,

The corresponding termcap is

> infocmp -Cr vt100
#       Reconstructed via infocmp from file: /usr/local/ncurses/share/terminfo/v/vt100
vt100|vt100-am|dec vt100 (w/advanced video):\
        :5i:am:bs:ms:xn:xo:\
        :co#80:it#8:li#24:vt#3:\
        :@8=\EOM:DO=\E[%dB:K1=\EOq:K2=\EOr:K3=\EOs:K4=\EOp:K5=\EOn:\
        :LE=\E[%dD:RA=\E[?7l:RI=\E[%dC:SA=\E[?7h:UP=\E[%dA:\
        :ac=``aaffggjjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~:\
        :ae=^O:as=^N:bl=^G:cb=\E[1K:cd=\E[J:ce=\E[K:cl=\E[H\E[J:\
        :cm=\E[%i%d;%dH:cr=^M:cs=\E[%i%d;%dr:ct=\E[3g:do=^J:\
        :eA=\E(B\E)0:ho=\E[H:k0=\EOy:k1=\EOP:k2=\EOQ:k3=\EOR:\
        :k4=\EOS:k5=\EOt:k6=\EOu:k7=\EOv:k8=\EOl:k9=\EOw:k;=\EOx:\
        :kb=^H:kd=\EOB:ke=\E[?1l\E>:kl=\EOD:kr=\EOC:ks=\E[?1h\E=:\
        :ku=\EOA:l1=pf1:l2=pf2:l3=pf3:l4=pf4:le=^H:mb=\E[5m:\
        :md=\E[1m:me=\E[0m:mr=\E[7m:nd=\E[C:pf=\E[4i:po=\E[5i:\
        :ps=\E[0i:rc=\E8:rs=\E>\E[?3l\E[?4l\E[?5l\E[?7h\E[?8h:\
        :..sa=\E[0%?%p1%p6%|%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;m%?%p9%t\016%e\017%;$<2>:\
        :sc=\E7:se=\E[m:sf=^J:so=\E[7m:sr=\EM:st=\EH:ta=^I:ue=\E[m:\
        :up=\E[A:us=\E[4m:

(The termcap name for blink is mb, which you can see in the description).

So... if you are not seeing blinking text, that could be (a) the terminal itself or (b) the terminal description.

Further reading:

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